On my shamans I always have trouble in all BGs but AV.

But on my Dk+rets I own pretty much every BG except SOTA which I only play when it's the daily and it usually takes me 1-2 tries to win it but I don't know if that the norm or I just got lucky.

The reason I do better with DK+rets than with shamans is because my DK is almost unkillable, it requires an entire pug or another premade of 5 + some extra pugs. On the shamans, even 3-4 melees can keep me rooted in place a long time, especially if they are rogues, and being stuck in one place means you can't support your team to do objectives.

But on dk+rets, even if I get attacked by several I can still keep dragging them with me towards an objective (e.g. flag carrier, base flag, etc.) and keep killing on the way, with shamans you can't do that.