Yeah, I've been really impressed with the healing ability of the DoK. While the others have some nice single target heals, the DoK seems to take the cake with the group heals. Having one in a group with two tanks and two mdps who stick close forms an effective wedge that is really hard to break up. The Dark Rites line is really awesome for this too, and after watching how sexy they can keep a coordinated group alive, I'm tempted to roll one.
I agree with what you're saying though, I see way too many thinking they're some sort of dps, when actually it looks like they should be pretty far from it. Since you mostly want to heal, and have to be up close, it seemed like Willpower is the way to go, followed by Toughness, Resists, and Armor, leaving little room for Str, though it doesn't really look needed.