Radical thought...remove the off-tank?

[Sylvina]

Unless your running unending coil all tanks should be gearing/melding to maximize dps nothing else hits hard enough to warrant any differently.

The time I was oneshotted through my cooldowns in O1s by twinbolt becuase I wasn't in tank stance when it came up says otherwise. Unless you already have an item level higher than whats required for the content, stuff hits plenty hard.