I'm using truenamers as bad guys in my game. I think the truname rolls hobble them pretty thoroughly. Lower level NPCs have to roll pretty high to affect PC, so they are reduced to a clumsy buff class. I have yet to try a higher level truenamer vs. my PCs: that might prove a little more of a challenge.
I suspect a PC truenamer would be very effective vs. lower level mook NPCs (lower DC to affect them), but have a hard time dealing with higher level BBGs (large number of hit dice in some monsters would make a truename check on them pretty futile).
The other two classes are more fun as villains, especially the Pact Magic types: they get fun, easter egg abilities. It looks like in order to really min max them, you should do some multiclassing. Higher level abilities aren't really scalable in that situation.