[Messianic]

It's not that they're not helpful or lazy - those are more player characteristics than class characteristics.

It's that they can't do anything at all which effectively acts as a force multiplier for a group. Their sustained DPS blows. Stuns aren't all that necessary or comparatively useful if the rest of the group is decent, and are a pretty huge manasink if you're doing anything except Tishan's clash. Even rangers have root, and do a good deal more sustained DPS. AoE nuking is almost never appropriate in a traditional, non-AoE group. Shadow step/Yonder are rather pointless unless you're in a hallway or really safe environment already; if you pull aggro, using those spells is one of the worst things you can do for your tank. Snare is adequate.

Basically, if you're looking for a 6th member, every single other class is a better choice, players being equal or player quality being unknown.