The class hardly fails, but I definitely agree that the +4 to UMD checks hardly makes up for the lack of imbue. Also solely lacking is the ability to trade feats for additional invocations, as well as spell-like ability metamagic feat equilavents. A few invocations were also gimped, like Wall of (less than) Perilous Flame.
Regardless, I still plan on playing a warlock, since it's the roleplaying decision I've made for my evil character, and I'm sticking to it.
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Actually a couple have been enchanced.
Warlocks get Shapechange in NWN2 it seems
Depending on the shapes, that might make up for the lack of enchanting for me.