First off Hal. I didn't SAY Energy draining. I said Ability score draining attacks. Like the Wis loss from being hit by Lamias. or the Str loss from shadows. Or the Int loss from brain eaters and Oblimax (memory moss).. There's others out there, and SOME of them are perm losses.
Arrrgghh! Either my eyes are going or my mind is going (must be my eyes - my mind got lost long ago! ), because I swear I saw the words "level drain" when you clearly wrote "ability drain".
And as for that tracking.. There's very little computing to worry about.. A little Prep work goes a long way. And we can do the same for mages.
With prep work, perhaps. But in the game it usually just happens suddenly. From experience, it's always slowed down the game dramatically because there are so many things that need to be changed and recorded, and often not every player has a PHB handy, so it gets passed around and takes time. I'd have to say, honestly, I've never found anything to slow the game down as much as level drains.