Lol. I think it may still be possible to save the escort if you take out the ranged ones and bodyblock the melee guys. Might not be worth it if you can't survive against the enemies.
This happens to me about once in every three or four trips through the Diakara. Usually its pieces of Harkon Zar. And if I'm really luck they're all gunslingers.
The good news is that after you get over the shock, you'll be surprised at what you can clear while keeping an escort alive. This is what those Healing Totems and Shield Wands are for. Slap one on asap if you've got one. Then, burn down that Boulder Thrower and you should be good.
I threw a spell at them, got hit with a rock that knocked me back and took out more than half my shield and killed the escort at the same time, then a one more opponent popped up climbing though the rocks.
I'll go back when I'm like level 40 or something. Till then, I have no chance at all.