ive never had to drill any cleats out, & ive seen some in a right state. it really is an act of desperation to drill anything out.
ive removed loads of stuck cleats over the years, mainly by using a pin, to completley clean every tiny piece of dirt that is wedged in the allen hole, then using a BRAND NEW allen key (not one thats even been used once!). using a cobblers last helps, but otherwise stick your hand inside, then its all about technique, apply tons on downward pressure, (sounds obvious-i know, but twisting to much is what rounds 'em off) & they should pop.