As a Paladin main I have a similar beef with my fellow tank in 8-mans. In my latest example I got Garuda HM in a trial roulette, and I'll start by hopping into Shield Oath because I was expecting to tank. Then my Paladin co-tank does the same, he pops Shield Oath. So I think "Oh okay, he wants to tank this. I'll just stick to Sword Oath and dps then. No problem." So I switch to Sword Oath. As everyone is buffed up and ready with Protect, Stoneskin, Adlo and you name it, my co-tank doesn't move an inch. He's just standing there in Shield Oath waiting. After about half a minute or so I swap back to Shield Oath and pull, and the guy comes after and begins dpsing with his Shield Oath still active... I've seen some Dark Knights do this while still in Grit as well.
Ugh. >_<