This isn't an exploit, but it's something that I could see Blizzard adjusting with just a small tweak; Make him throw up his 99% shield at 70% regardless of what he is doing at the moment.
But exploit? Not really. The fight just has a lenient enrage timer, and low raid damage in p1 if you're slaughtering all the oozes and eating a puddle here and there. This allows people to durdle for 8 minutes :P