I have off-tanked this fight many many times and I never provoke first, maybe our strategy is weird but it hasn't failed us yet. Since it never goes to the off tank I let it stay on whoever it attaches to (or mt can provoke if you want). Once it reaches 2 stacks I provoke it and throw a tomahawk or two at it, then I just proceed to heavy swing until it is at 1/3 health. Even healers can't take it from me. The only danger is if someone accidently attacks the spiny before I provoke as it makes it harder to get enmity.

Another tip: If your dps does not kill suprana before they jump, you can tank limitbreak with 1 bar to save your party. Use the LB just after they jump and only use the LB if your ranged can't kill it in the few seconds you have when they appears in the middle of the map.