What exactly is the problem with Concentration? I have a paladin in my game now and even with concentration he doesn't seem to be lacking in power... or is there another issue at work here?
Imaro:
It's a paladin thing: many of his smite spells require concentration, which conflicts with other buffs like Bless.
Might be a little off topic, but do I understand the "smite spells" correctly? You concentrate on it, you hit, you deal extra damage and the spell ends? Or can you concentrate on it even after dealing extra damage and deal that damage again?
As long as both PCs and casters are limited to not tons of buffs, how would this be NPCs working differently? Concentration is actually a really good thing for limiting one of the biggest problems with NPC casters in 3rd edition.I also think that this is a good thing for NPC casters to multi-buff and I hate the whole "Well, it's an NPC, it's allowed to work with different rules" concept. I like a world where the physics of magic work the same for PCs and NPCs alike. I want dragons or archmages to have 3 buff spells up to help thwart the plethora of stuff that PCs can throw at them.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.