It's a shame you're both pt tanks, IMO assassin tanks are the kings of that fight due to shroud and phase walk.
My group does the strategy you designated "a," the tank on the hand that pops the first shield runs to the far hand, and the tank that was on that hand runs in to clear stacks. At this point, the tank that was on the far hand should do their best to manage orbs that the other tank can't get, by using stuns, knockbacks, and taunting/popping those that won't kill him/her.
After the second shield comes up, everyone clears stacks once again, and then both tanks cc/pop orbs while the dps gets brontes down that last bit.