I wish they kept a changelog of the actions (including added and removed actions) on the FFXIV job pages. You can still retrospectively piece the timeline of changes together if you put in some effort, but it should be a lot more transparent to the end user.

The raidwide heal on Shake it Off and Divine Veil was added on Endwalker's launch (02/12/2021). It's a bit of a strange decision for starters, because they were already superior to Dark Missionary and Heart of Light. The regen effect on Shake it Off looks like it was added on 10/01/2023, which would have been Patch 6.3. It's a bit of a strange choice because bubble shields can absorb damage from DoT ticks as well as of this expansion.

I think what they need to do is just put all of the tanks' raidwide mitigation side-by-side. I'll do it now.

Paladin:
Lv. 56. Recast: 90s, Range 30y.
Creates a barrier around self and all party members near you that absorbs damage equivalent to 10% of your maximum HP. Duration: 30s.
Additional Effect: Restores target's HP, Cure Potency: 400.

Lv. 70. Recast: 90s, Range 8y.
Increases block rate to 100% and creates a designated area in a cone behind you in which party members will only suffer 85% of all damage inflicted. Duration: 18s.
Effect ends upon using another action or moving (including facing a different direction).
Cancels auto-attack upon execution.

Warrior:
Lv. 68. Recast: 90s, Range 30y.
Creates a barrier around self and all nearby party members that absorbs damage totaling 15% of maximum HP.
Dispels Thrill of Battle, Vengeance, and Bloodwhetting, increasing damage absorbed by 2% for each effect removed. Duration: 30s
Additional Effect: Gradually restores HP. Cure Potency: 100 Duration: 15s.
Additional Effect: Restores target's HP. Cure Potency: 300.

Dark Knight
Lv. 76. Recast: 90s, Range 30y.
Reduces magic damage taken by self and nearby party members by 10%.
Duration: 15s.

Gunbreaker:
Lv. 64. Recast: 90s, Range 30y.
Reduces magic damage taken by self and nearby party members by 10%.
Duration: 15s.

Looks balanced, right? It's especially funny when you remember that Dark Missionary and Heart of Light were introduced one expansion later. This is the same balance team that actually thought it was 'balanced' for a tank to be down 1-2 raidwide mitigation actions compared to the others.

If they want a fair gameplay experience, they have to go back to the drawing board and redesign these abilities. The easiest solution without any bloat is to just remove all of them and have tanks rely exclusively on Reprisal, which is supposedly why it was handed out to every tank job in the first place. If you don't want to do that, the alternative is to create four unique actions that each provide a different benefit. For example:

Passage of Arms:
Increases block rate to 100% and creates a designated area in a cone behind you in which party members will only suffer 90% of all damage inflicted, and prevents draw-in and knockback effects. Restores HP over time. You may move into this area once activated.

Divine Veil: Removed.

Shake it Off:
Increases maximum HP of self and all nearby party members by 10% and restores the amount increased.
Dispels Thrill of Battle, Vengeance, and Bloodwhetting, applying the following effects:
Thrill of Battle: Healing actions on self generate healing on nearby party members.
Vengeance: Increases maximum HP of self and all party members by 2%.
Bloodwhetting: Restores additional HP to party members for every weaponskill delivered.

Dark Missionary:
Creates a personal barrier around self and nearby party members that absorbs damage totaling 10% of maximum HP.
Grants Dark Bond: Increases movement speed by 10%. Effect can jump to a nearby player. You cannot reacquire Dark Bond once it has been passed on. All players receive healing proportionate to the amount of times this effect was passed when it expires.

Heart of Light:
Creates a field in which absorbs incoming raidwide damage proportional to the number of players inside. Any damage in excess of the total is split equally between players within its area. When the effect ends or the barrier shatters, restores HP to all nearby players.

Either way, they should do a formal review of the raidwide mitigation tools on tanks and either reduce it to one unique job specific action each or just stick to Reprisal in isolation. And the magical damage only criteria needs to go.