I never bother trying to tank the casters. I just set my shaman to target them first, and while the captain america shield is flying through the air they begin dpsing them. I tend to kill the casters first while my pala is tanking the others, gives me more time to build up a nice threat cushion for nuking.

Only issue I had with Ramparts was remembering to do everything when playing with the last boss. Once that was figured (and I was level 62 which helped), it was fine. BF was child's play in comparison.