I got Kenny the day before yesterday, and my findings are pretty much the same. I expected that with him being "elite", he would be a fairly rocking healer (for a merc), but that's not really the case. He can tear through heroic enemies with his dps, and his HP is awesome, but when it comes time to heal, he doesn't feel much more powerful than a normal merc. Granted, I have been throwing him against contested Skyshrine while solo, but I was a tiny bit underwhelmed with the heals. I wouldn't mind seeing those given a slight buff. The way I remember cleric mercs in EQ1, they would heal you as soon as your health started dropping, but Kenny will wait until you're in the red to do anything about it, which is often times too late.
As for cures, it was stated before they have none, like was said above, so I was expecting that. I just make sure I always have my pots stocked. No merc will cure curses, unfortunately, but other detriments are easy enough to deal with. Still, having a lot of fun watching him tank heroics and stab them to death with that tack he carries.