From what you wrote you are way over prepared for Bonemass (meaning it should be a walk-in-the-park) considering all you need is a banded shield, iron mace and poison resist potions to take it down.

Given how raids work I would personally not be using them as the primary criteria for deciding on my next action.

And as @Rhapsody mentions without the wishbone looking for silver becomes a bit more work (and it also makes you more of a target because of the extra noise) so you may end up retracing your steps in the Mountains once you do get the wishbone.

Also the block is what saves you not the parry when fighting Bonemass. You cannot stun it and although with no parry you lose some damage potential it is still easy enough to face tank down.