Crippling strike is AoE + AoE debuff, at 3 AP it would still be very beneficial to use if you can hit more than 1 target (which should be the case with most AoE skills, they should not be good for single target damage). Maybe it can have bit higher damage modifier than battering ram cause no mobility and not as good at CC.
High damage skills should be the ones that have little utility, and AoE skills should not outdamage single target ones (like it happens with crippling strike compared to many other skills).
Here's my opinion - there should be single-target skills and AoE skills, and obviously single target should deal more damage, however I believe that ALL skills should always be better than a simple auto attack in EVERY way. Skills require memory and have a CD you use them only once in a few turns and some also require more AP, so it's justified.
