**Revenant.** Guardian can't destroy enemy boons, rev can. Other than that Rev can do anything a guard can - power dps, condi dps, healer, support, tanking.
Blighter's Boon is fine if you ask me - it's a sustain trait, not an offensive one. As for deadly chill, yeah there a buff is in order. I would think for example increasing condi duration on chilled targets.