There are two options. 1 is to single tank the fight so that the Mutilated Corruption dies before the second impale. Remember that your DRW gives you an additional 20% avoidance. So make sure you save your RP and runes for a healthy Blood shield and 60RP for DRW before the impale. You can use a priest for pain suppression or guardian spirit every other platform, using IBF on the alternating ones. What we did on the platform right before head phase is have a ret pally soak the second impale during the elementium bolt. What we'd do is I would stay up next to the Mutilated corruption about 3 seconds longer than the group that was stacking away from the bolt coming down with the paladin so that he'd get aggro/impale and I still had time to run back and stack with the group. Then we'd pop divine hymn while the bolt was being dps'd on the platform.
Also, it's good to save your 4 piece VB CD for raid during that time that everyone is being hit so hard by the bolt's AoE on the ground.
If you're 2 tanking it there's no reason you can't pop IBF every time for impales. Or use the Valor trinket and alternate that with IBF. AMS should always be up for that as well as your DRW and if you've glyphed VB, you'll have increased heals received by 15%.
Since you don't have a priest healing you should be 2 tanking it. Priest heals are OP for this fight. Good luck.
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