Rampart - fine as is.
Anticipation - trash-tier. Completely useless outside of 4-mans, and even then only situationally useful.
Shirk - Great addition to end-game tanking. Being able to use it to stack emnity OR to force a tank swap onto a slow OT is great. Trolling use also a plus for funsies with friends.
Awareness - solid for what it is. No complaints on it's effectiveness but a lower CD (90-100s) would be nice, given how niche crit immunity can be.
Conv - another solid one. No complaints or changes needed.
Low Blow - Just keep the native stuns for DRK and WAR. Remove their potency if you have too. Trying to remember to take Shirk off my bar in a 4-man and replace it with LB, then swap the two again in 8-man content is ridiculous.
Interject - useless. There's nothing this skill does that a stun can't do already. Only the stun will work on anything, not just magic.
Ultimatum - useless. I suppose it may have niche use as a "backup" provoke in case things go south and provoke is on CD, but there are no situations in game where generating snap aggro in an aoe situation requires a provoke-like skill. Current aoe emnity skills are more than enough.
Reprisal - solid skill, hampered by it's CD. Keep the duration where it is at 5s, but lower the CD to 45s. You won't see tanks spamming it (i.e. trying to keep it up as much as possible on CD), but it will become easier to coordinate between two tanks to mitigate raid-wide damage.
Provoke - no comment. It's provoke. Duh.
My Suggestions
Scrap Low Blow; bring back Brutal Swing/Low Blow as native skills to WAR and DRK. Ditch Ultimatum and Anticipation completely. Lower the Cd on Reprisal, and either give Interject some use, or remove it as well (my preferred option).
In place of Ultimatum, Anticipation and Interject, add in a role action that functions as a charge. 0 potency, 30s CD, adds emnity on par with Flash. This gives PLD a charge options, and allows DRK and WAR to grab another oGCD charge for further mobility and/or threat gen (not like threat gen is needed really, but if you make it an early level role action then it's something that can help up-and-coming tanks). For the second role action, add in Bloodbath. Carbon copy it from the DPS role ability if you have too. 20s is fine, although I won't lie and say calling it Bloodshower and making it 30s would be great to.
Finally, add a final new role skill, "Protectors Gambit." 150s CD that resets the CD on Rampart, Sentinel, Vengeance and Shadowskin, at the cost of lowering the tanks damage dealt by 5% for 15s. The idea behind this skill is essentially a mulligan in higher-end or progression content, while also still providing a good deal of usage in smaller group stuff, say with large aoe-focused pulls, or during world content such as hunts or FATE's.