Re: Countering Master Enslave...
 

That's not bad for the abusive end game spells, but could be irritating to apply to the less potent early game ones. I'm particularly thinking Divine Blessing. Fanaticism and the various national undead buffs as well.
You could just exempt them, I guess.

Re: Countering Master Enslave...
 

Is the problem some of the endgame spells in general or master enslave in particular?
If it's just master enslave; then just address the issue in the simplest way possible: changing master enslave.

If it's in general; then i'd like a full list of the offending spells to deal with.
Perhaps the problem lies with spells that are battlefield but only hit enemies? changing such to high aoe might cover it.

It sounds like many of these issues could be addressed by spell modding easily enough.

Re: Countering Master Enslave...
 

I like your train of thought Twan. One based purely on AP +rnd would be very nice. Certainly there would be debate on whether it would be base AP, base AP+ any "natural" quickness or as above + spell casted quickness + magic items...
-SSJ