I can't deal with the exp penalty of Iksars. Period. All it means to me is more reps. More reps means more mindless repetition and to me that makes the game less fun.
Not only that, but lifetaps and lifetap DOTs are practically irresistible so that automatically makes them a part of my DOT stacking spell selection at all levels. I'm going to use them anyway so the fact that an iksar uses them less often is no issue to me. The mana you waste by casting double-save DOTs that get resisted 50% of the time instead of lifetaps is going to slow you down in the long run.
So no, I really don't care about Iksar regen. Maybe for monks and shaman it's a game changer but the exp penalty isn't worth it to me and it's not even a consideration.
My Project 1999 video playlist