You guys should actually try the ability before bashing him for "as others abilities" ^^

There are three problems combined. First one is, as you said, that you need to wait for previous animation to finish. Second is the lattency of the server. Third one is that still, the ability take a frigging second to take effect due to a super long animation of its own. This is INDEPENDENT of the two other problems, and akin to what happens with other long animation effects like raise and LBs.

All 3 combined can indeed make it look like the ability take forever to go off, and make you put the ability on colldown while still dieing an embarassing proportion of the time. All in all, it is a good thing encounters are super scripted, because if you are not able to plan several second in the future by saying "the boss is going to use this soon, i am low on health, the healer is probably not going to have me topped off in time, i need to stop what i am doing and be ready to use it if the healer doesn't make it in time", then it will be useless.

If the intent is to give you an oh'shit button allowing you to avoid an unexpected death, the effect is missed by a mile and a half. The only use of the ability, as a consequence, is to cover up for healers being overloaded (still great, but, yeah).