i didn't play much in WoD, and with exception to WoD, i've always switched between bear/rdruid, and disc/spriest but i haven't played with either of them since the legion patch.
will be more on the casual side. cbf to hardcore raid anymore.

which should i main? i'm torn

Im playing holy priest this xpac.

I mean idk what you like to play role-wise but if u have even a small desire to tank maybe roll druid. Also afaik dudu heals and shaman heals are looking best for PVP. not that priest is bad.

I wouldn't roll a druid in Legion.

LOVING my enhancement shaman. going holy pally next.

Druids are faceroll, Priest you may need to think a bit. Depends what you want to do.