Cover?

[Maelwys]

Then the off tank will hallowed ground and cover the main tank.

Doesn't work.

See Above.

([Bulwark --> Cover --> Sentinel] works though!!)

We used a strategy on Turn 4 last night to beat Phase 4 down quickly - 2x BLM, 2x BRD, 2x PLD, WHM, SCH.
Each Paladin took a Black Mage and Covered them whilst they AoE nuked the Rooks and Spiders.
If Cover wore off before they finished off the last bug, they could use Manawall for the last hit or two.
Saved using all our MP on Flashing the Bugs (meaning more for phase5/6!) and meant we could hold aggro on the Spinner Rooks better to dodge pox.