I'm not too fond of relying on Bulwark for big hits myself. Crit Rip doesn't happen often and for the rest of the fight, it's mostly fluff damage. Depending on how fast your group pushes the phases, you'll only get 2 crit rips in phase 1 and another 2 in phase 3.
During phase 2 (or adds phase), however, it's a slightly different story. When the 2 sons and 2 daughters appear, the prey mechanic comes with it. This means that one healer is occupied for ~4 seconds or both healers are occupied for ~2 seconds (varies depending on how it's being handled).
Bulwark has more value to use for the adds here, simply for the fact there are two targets attacking you for a lot of fluff damage, rather than needing it for one hit which may or may not be blocked. It's still RNG based, regardless. On average, it should help the healers out a little bit here. Also, if bulwark fails to proc on Crit Rip and it happens to kill you, it's all over.