Does anyone have any tips for a lvl 45 BLM attempting this instance?

What is the best course of action to take out as many of the the Planar Fissures as possible in the short time we have? Is it better to take them out one by one? Which spell is the most effective?

I tried using Sleep on the mobs, but there are just too many, so I can't manage, as hard as I try.

I managed to get past the second wave with some difficulty, but I couldn't do anything in the third wave. I died almost instantly when all the mobs swarmed on me.

Any tips would be welcome.