I think this depends on whether the enmity system stays the same as it is now. If Provoke and Ultimatum give you more than enmity + 1, or if the enmity threshold for taking back aggro is higher than 100%, then you could see Ultimatum used as a snap enmity grab as well. You could then switch over more quickly to AoE spellcasting on PLD, for example, without needing to Flash, because you'd know that the mobs would be locked on you until the dps surpassed your enmity by a set threshold.

From another perspective, if Shirk is an enmity transfer tool (i.e. shirking your responsibilities) as some people are speculating, then you could theoretically pass aggro between two tanks through Shirk alone, without needing Provoke. But if you have to pass a threshold to regain enmity, then they both fill different niches.

Anticipation actually looks a lot like Dark Dance, so I wouldn't be surprised if it's a parry rate skill. Awareness might not even be the same ability, or it may have other effects added to it. For example, it could be a combination of Critical Hit immunity and the Tempered Will effects.

We don't have tooltips for Rampart, Provoke, Anticipation, Awareness, and Shirk. We can make some assumptions, based on the names, but we can't take anything for granted, even if they share the same name and icon as actions currently in the game.