try to have better positioning before you begin casting, dont stand close to your targets and try to cast something unless u know your gonna get that cast off cause they can easily just go behind u, start casts with your back to the wall or at a medium range so they have less chance to walk behind or to the sides of you. Some people have had luck with controllers using the auto target, i believe default is to click in on the a control stick? iirc, or numpad 5 on keyboard,

most blm i run with, wont try to dps until they get everyone slept, using the aoe sleep at times when u can get 2 or 3 people at the same time. When they do dps they will just cast fire 1 and hope they get a proc, but sometimes blizzard or other things happen as well, I'm sure someone else would be better qualified to explain their "rotation"