It depends to the tank by a large margin. Gladiators stun eg. is for interrupting spells but the Marauders stun is a very good tool for mitigating damage and should be Held on CD unless rupting is mandatory. Also the Gladiators CD´s are obviously good - so they use them. Marauders are similar good but they tend to either don´t use them or all in them instead of cycling them.
My observations as leveling the healers.
Gladiator is imortal. Marauder is fine.
My observations as leveling the tanks.