My main concern and keep in mind this is theory rather than actually observing it in play is the advantages of Warlock are unlimited range attacks of magic and abilities. The disadvantages are that the damage isn't what a melee build can put out and the spells are not as potent as what a Wizard can put out.
The concern is that due to how the dungeons are built 'unlimited arcane power' isn't a massive selling point considering that the dungeons for the most part have rest points (sometimes multiple ones) and there are a lot (I mean an awful lot) of spell slot items available to Clerics, Wizards and (I think) Druids. I have literally never once run out of spells for Requiem in any Dungeon on this server (except ninth level ones - who hasn't?). Then add to this the mansion spell which while granted does not work in every dungeon but it works in quite a few and replenishes all those multiple spell slots just in case I start to go a bit trigger happy for the lulz.
The unlimited spells would be quite cool but the spell selection is limited to the point where it would make for some very effective tactics concerning darkness spamming coupled with sneak attacks (Devil's sight, Darkness, Walk Unseen and See the Unseen) but very little else.
In fact the whole spell selection seems to make you a tougher melee combatant (for the aforementioned darkness spamming) with Dark Foresight, Word of Changing, Aura of Flame and Starless Void all giving you a damage shield or additional HP. While all of those except Dark Foresight are pact specific it means every choice gives you some form of increased melee ability. Indeed even the Greater Dispel (which is pretty cool) is touch range meaning you have to get in close.
The class has some nice battlefield control spells (which is my favourite type of spell) mostly linked to the Fey Pact and Star Pacts - Bewitching Blast, Eyebite, Will of the Feywild, Frightful Blast and Doomsayer being the pact specific ones with draining blast being the essence you can apply to your Eldritch Blast.
I have not mentioned Utterdark Blast in the above because negative levels on CD is a fairly useful ability for PvP but against normal monsters you're often just better off doing anything else because you have to usually target the monsters strongest save (fortitude) and the monsters tend not to last long enough for your spell to have done much good, as opposed to either incapacitating it or contributing damage of your own along with the fact a lot of the boss monsters are immune to negative levels.
However I think it shows really good design to have the fear, confusion and dominate as single target spells because it makes the unlimited ability useful without the mental broken of it being mass targeting it just seems a shame you need to pick either Fey or Lovecraft to do it.
The other thing this class doesn't seem to do well is play with others. It has no buffs (except Ultravision . . . woo) and I am not sure it would be out of place for it to have some party buffs like the mass-animal spells, death wards or emotion spells which gives them something to contribute as a little bit more unique. Dispels are much more common now and the party member that can help keep a party on their feet (with much needed buffs) would fit a more unique role. Some of its abilities are counter-intuitive to party play - Tentacles is an amazing spell but it rarely gets any use because it takes a lot of work and effort to make it work within a party dynamic and can often mess up your combat orientated friends. Likewise with the cone and radius versions of the blast these are going to be difficult to target in the hectic fast moving world of NWN without hitting your buddy in the face. If they're not already can they be made to only hurt enemies and not allies?
My other question is with Eldritch Blast do you have to constantly click and target it at your target (every round) or can you click and forget?
I certainly think the class is neat and the critique above is meant to just be constructive criticism I understand it is very easy to say from my sofa - code X, Y or Z and not understand the implications of it from a work/scripting perspective.
My other fear is that this class is a very, very nice dip class for rogue the first four levels are like a wet dream for them. Unlimited Darkness, Unlimited Ultravision, Auto-10 on UMD and a small defensive buff with entropic warding (which needs to be buffed as an aside). That is an amazing dip.
As a suggestion (rather than just point out things) could the spell selection scale after certain milestones of Warlock. So See the Unseen goes from basic See-Invisibility up to True Sight at high enough level. Darkness turns into 'Biting Darkness' that causes damage to anyone without Ultra-Vision/True Sight. Entropic Shield gets stronger as you level slowly adding AC, Deflection and Displacement. Flee the Scene turns from Dimension Door to the option to use it as a teleport to a mass teleport. Devour Magic adds AB/AC bonus depending on if the dispel was successful (no idea if this is actually possible to be scripted). Dark Foresight adds neg energy protection and boosts saves as your Warlock gains in levels.
The concern is that due to how the dungeons are built 'unlimited arcane power' isn't a massive selling point considering that the dungeons for the most part have rest points (sometimes multiple ones) and there are a lot (I mean an awful lot) of spell slot items available to Clerics, Wizards and (I think) Druids. I have literally never once run out of spells for Requiem in any Dungeon on this server (except ninth level ones - who hasn't?). Then add to this the mansion spell which while granted does not work in every dungeon but it works in quite a few and replenishes all those multiple spell slots just in case I start to go a bit trigger happy for the lulz.
The unlimited spells would be quite cool but the spell selection is limited to the point where it would make for some very effective tactics concerning darkness spamming coupled with sneak attacks (Devil's sight, Darkness, Walk Unseen and See the Unseen) but very little else.
In fact the whole spell selection seems to make you a tougher melee combatant (for the aforementioned darkness spamming) with Dark Foresight, Word of Changing, Aura of Flame and Starless Void all giving you a damage shield or additional HP. While all of those except Dark Foresight are pact specific it means every choice gives you some form of increased melee ability. Indeed even the Greater Dispel (which is pretty cool) is touch range meaning you have to get in close.
The class has some nice battlefield control spells (which is my favourite type of spell) mostly linked to the Fey Pact and Star Pacts - Bewitching Blast, Eyebite, Will of the Feywild, Frightful Blast and Doomsayer being the pact specific ones with draining blast being the essence you can apply to your Eldritch Blast.
I have not mentioned Utterdark Blast in the above because negative levels on CD is a fairly useful ability for PvP but against normal monsters you're often just better off doing anything else because you have to usually target the monsters strongest save (fortitude) and the monsters tend not to last long enough for your spell to have done much good, as opposed to either incapacitating it or contributing damage of your own along with the fact a lot of the boss monsters are immune to negative levels.
However I think it shows really good design to have the fear, confusion and dominate as single target spells because it makes the unlimited ability useful without the mental broken of it being mass targeting it just seems a shame you need to pick either Fey or Lovecraft to do it.
The other thing this class doesn't seem to do well is play with others. It has no buffs (except Ultravision . . . woo) and I am not sure it would be out of place for it to have some party buffs like the mass-animal spells, death wards or emotion spells which gives them something to contribute as a little bit more unique. Dispels are much more common now and the party member that can help keep a party on their feet (with much needed buffs) would fit a more unique role. Some of its abilities are counter-intuitive to party play - Tentacles is an amazing spell but it rarely gets any use because it takes a lot of work and effort to make it work within a party dynamic and can often mess up your combat orientated friends. Likewise with the cone and radius versions of the blast these are going to be difficult to target in the hectic fast moving world of NWN without hitting your buddy in the face. If they're not already can they be made to only hurt enemies and not allies?
My other question is with Eldritch Blast do you have to constantly click and target it at your target (every round) or can you click and forget?
I certainly think the class is neat and the critique above is meant to just be constructive criticism I understand it is very easy to say from my sofa - code X, Y or Z and not understand the implications of it from a work/scripting perspective.
My other fear is that this class is a very, very nice dip class for rogue the first four levels are like a wet dream for them. Unlimited Darkness, Unlimited Ultravision, Auto-10 on UMD and a small defensive buff with entropic warding (which needs to be buffed as an aside). That is an amazing dip.
As a suggestion (rather than just point out things) could the spell selection scale after certain milestones of Warlock. So See the Unseen goes from basic See-Invisibility up to True Sight at high enough level. Darkness turns into 'Biting Darkness' that causes damage to anyone without Ultra-Vision/True Sight. Entropic Shield gets stronger as you level slowly adding AC, Deflection and Displacement. Flee the Scene turns from Dimension Door to the option to use it as a teleport to a mass teleport. Devour Magic adds AB/AC bonus depending on if the dispel was successful (no idea if this is actually possible to be scripted). Dark Foresight adds neg energy protection and boosts saves as your Warlock gains in levels.