It took me many wipes to get it figured out but I can do it now with ease. I'm running WMMMP and the key for me is sheeping. I have a keybind that will assist the tanks target in a round robin fashion on my mages. So I click mob #1 on tank (which I drive from) and hit that keybind then target #2 etc until all three mages have a different target. Then I have a keybind to hit polymorph on all mages at the same time.

Getting the pull order in that first main area before you enter the scarlet side takes some practice. The key is not to get runners so I pull way back or counterspell casters to get them to run to me. Once inside I have a general rule to always pull back to the previous corridor. I'll move ahead with my tank after having the rest of my group positioned in the previous corridor. Then I'll target and assist to get my mages selected on the targets they need. This way they don't have to actually be able to see the mobs only my tank does. Then I'll pull the mobs with a bow shot into the previous corridor and sheep as soon as they are in line of sight of the mages.Then I'll start burning them down one by one. When that group is cleared I'll drink with the mages and immediately start running to pull the next group with my tank. Very little actual downtime this way. Once I got the hang of it I can do a run in about 50 minutes. Not nearly as fast as some of these other guys but its safe and consistent.