1)Dark resists to avoid getting lifted
2)Just run through the gate
3)Snipe from the stairs

The enemy spell chuckers are usually on the other side of the cyclops. I run out past the cyclops face R and nail the spell caster with a bow. As for the rest, it's use the stairs as a hide-n-shoot process or simply run like ____ past everything and get into the hallway leading further into BBI. You'll find a sanctuary and can repair a rift stone to get the pawns back that failed to follow your lead and got themselves whacked.

The mages are annoying but what I always did was get them to cast maelstrom in the doorway down below, then run back up and leap off the ledge. The fall damage doesn't matter. There will often be garms spawning down there and working together, so that's risky, but the casters never stop with the maelstrom. I'm playing melee exclusively so I don't have the benefit of shooting anything in this room.

So, you either get the garms to spawn before the maelstrom appears in the doorway, and lead the garms into the stairwell to kill them all there, or even upstairs with your pawns' help. Just don't get too close to the door or your pawns are going to go jump in the tornado and get instakilled.

Or...

If you want to "cheese" this encounter, eliminate the flyers and you have nothing to harass you after you jump down. If garms spawned, run to that corridor where the leapworms come out of the crawlspace. Spam F2 to get your pawns to teleport over there with you, since they won't jump off that ledge. In the crawlspace, garms can't reach you, so you have some time to think and get yourself in order.

Now you have the option of fighting the garms in the corridor leading to the crawlspace, or going all the way up and jumping down, grabbing the prisoner cyclops to prevent fall damage on the way down. The casters are defenseless at this point and if their spam of spells has woken up a prisoner cyclops you can go through the door and come back, and he will be in chains again.

If you are brave, whittle the garms down and use an XP boost item, then kill them all at once.

The others posting above are right in stating you can just run past. The fighting part is entirely optional. I did it because I needed upgrade items and the XP was too much to ignore.