I'm not stuck, I just did it with what I thought was cheese but apparently is how you're supposed to do it, which is kinda stupid imo. If they're all together, it doesn't matter how fast you're moving (I have 15 hard points in rapture but as baal you're retardedly fast anyway), they're all going to spam their skills and sooner or later one of them's going to get a lucky shot in, assuming the huge aoe ones don't chunk you first. I had to kite them out of the valley of snakes entirely so they could get caught on the walls of the ruins in the lost city; and then I didn't even kill all of them, I just got talrasha himself far enough away from the mages that they weren't in range to make him invincible