Another thing I found helpful is how I pull and what CAs to use.
In a group like that I try to rotate my big spells (actually most groups).
Use Destruction One fight, and Open Wounds the next. The INT AA line down to the 30 percent recast helps quite abit. Use Jaggurnaught as it is up during the battle -typically not on pull, unless you are trying to show off your dps - not that I ever did that
Destruction before the pull (since its a long cast, and is a trigger based spell anyhow.
Assuming you mean multiple mobs on pull : {Destruction or Open Wounds}, Single tuant, group taunt, the damage taunt, my blue and/or green AE damage, continute attacking until group taunt back up, and cycle through most of your CAs. Try to keep the mobs close together if you can, this allows you to hit more at once. Also, try to keep them infront of you, this helps with your reposte (assuming you took the stamina line).
I typically do not cast my two blue ae damage spells back to back, since they have a long recast, they can also disrupt your standard melee weapon. I'll usually get an extra CA or two between the two blue CAs.
If there is room, especially if its a name, use Insolence Gibe.
I almost never lost agro. If you are loosing agro you may want to point out to the group, that you need time to position the mob and flip. Have them not engage until the mob is flipped for at least 1-2 seconds. You then have more time to build up aggro, you also determine how long it takes you to flip the mob.