This. The second a scarab mount is hit, it burrows. You'll be dismounted and surrounded. While it's funny the first time, to see an 85 flailing about, it gets really annoying when you are trying to get through this. Once Fankriss is dead, only half the bugs respawn in the gauntlet and, once the twins/C'Thun are defeated, none do. That makes the run back for those who die to C'Thun and want to talk to the dragons at the end, easier.

This is an annoying raid to get out of particularly when you have to go all the way back to the front to turn in your insignias. The dragons at the end (Brood of Nozdormu so they look like humanoids.) take some of the loot for tier pieces. As you're looking at C'Thun's room, they are around the corner to the left. If you are interested in collecting the pieces for 2.5, I strongly recommend doing them first, then ride all the way out and turn in your insignias. Whatever is left from the people at the front will be easy to get and, if you have a group that can't get past the twins, you'll feel like you've accomplished something. We've had people park an alt at the beginning of the raid to mass summon people to the front which makes getting backand forth possible.