To me, Punk DOES stand out from other heels, even the top ones. Most heels right now simply play the cocky arrogant type. Punk is probably the most sadistic and cruel heel i can remember since Triple H circa 99-01. The only ones who come even close to that are Wade (hands-off, let my boys do the work) or heel Edge (more of an opportunist and manipulater than sick and twisted). Kane is an other-worldly monster type character which is different.
You're assuming all heels are the same. And i don't believe at all that any good heel needs to have even a positive W/L record to be over. Kane, irrelevant he may be, still gets immediate reactions as a heel, which probably wouldn't have changed even if he wasn't booked to beat Taker as many times as he did last year.