I think that’s a mitigation and timing issue.
Memorize this pattern. On the first annihilation you could even make do with 1 ironfur, and if you’re using ursoc (and i prefer it) incarnation you’ll be super safe. You’ll have free healing with low CD frenzied regen anyways.
If you see annihilate come up you can use an orb to prepare yourself real quick. Or/and use it to get yourself back up immediately. If Kruul is near death don’t be afraid to be liberal with orbs.