The 30% dmg reductions abilities are not copypasted Rampart! If you have to mitigate multiple tankbusters in succession on min iLvl, Rampart just wouldn't cut it. And most "short recast" CDs (e.g. Heart of Stone) have a way too short duration to mitigate multiple tankbusters.

e.g. Titan Maximum Dual Earthen Fist/Earthen Anguish tankbuster into Megalith tankbuster. On min iLvl Rampart is not enough, even 30% would barely keep you alive (I remember the first week runs we had, even with Rampart+Nebula I dropped to ~10% with AA follow-up).

You need 30% mitigation, how you're going to map them is up to your party/tank.

Sentinel had to be changed to compete with the other "higher mitigation" abilities. 40% was overkill, and 3 min recast was way too long. It's a relict from HW where PLD struggled against multiple magical tankbusters because of Sentinels high recast time.

Vengeance had to be nerfed because it was overpowered. And honestly, they should remove the spike effect and just buff a few skills instead.