Yeh DHs remind be some how of Ret pallies on live, Good during poped cds, suck outside of them and very very soft.
I mean DH cant even be an FC, since their survival kit is very poor, i can't even picture what niche will DH have in RBGs other than maybe fast nod caps??? and its a BIG maybe.
At it's current state havoc doesnt have place in an rbg sadly. As stated before - no self sustain , easy to counter and seen by every1 10000000 kms away burst ( meta ) and outside of meta you hit like a noodle.
Vengeance can find a niche with pretty usefull sigils and being a mobile flag carrier probably