A cheat sheet for single-target tank mitigation.
Holy Sheltron, Bloodwhetting and Heart of Corundum are strongest during the first 4 seconds, so using them right before a heavy hit gives the best mitigation.
Rampart also raises healing received, so pairing it with a cooldown that heals increases the healing and makes you noticeably harder to kill.

Role actions

ActionRecastTargetEffect
Rampart90sSelfMitigation: 20% / 20s
Healing received up: 15% / 20s

Paladin

ActionRecastTargetEffect
Holy Sheltron5sSelfMitigation: 15% / 8s
Mitigation: 15% / 4s
Heal: 250 / 12s (1000)
Confiteor combo60sSelfHeal: 400 × 4GCD (1600)
Bulwark90sSelfBlock: 100% / 10s
Guardian120sSelfMitigation: 40% / 15s
Barrier: 1000 / 15s
Intervention10sOne party memberMitigation: 10% / 8s (20% / 8s while Rampart or Guardian is active)
Mitigation: 10% / 4s
Heal: 250 / 12s (1000)
Cover120sOne party memberTakes the damage in your stead / 12s

Warrior

ActionRecastTargetEffect
Bloodwhetting25sSelfMitigation: 10% / 8s
Mitigation: 10% / 4s
Heal: 400 / WS (1200)
Barrier: 400 / 20s
Equilibrium60sSelfHeal: 1200
Heal: 200 / 15s (1000)
Thrill of Battle90sSelfMax HP up: 20% / 10s
Heal: 20% of max HP
Healing received up: 20% / 10s
Damnation120sSelfMitigation: 40% / 15s
Heal: 300 / 15s (1500)
Nascent Flash25sOne party memberMitigation: 10% / 8s
Mitigation: 10% / 4s
Heal: 400 / WS (1200)
Barrier: 400 / 20s

Dark Knight

ActionRecastTargetEffect
The Blackest Night15sSelf / one party memberBarrier: 25% of max HP / 7s
Oblation60sSelf / one party memberMitigation: 10% / 10s
Dark Mind60sSelfMitigation: 10% / 10s (physical)
Mitigation: 20% / 10s (magical)
Shadowed Vigil120sSelfMitigation: 40% / 15s
Heal: 1200 (when HP falls below 50%, or after 20s)

Gunbreaker

ActionRecastTargetEffect
Heart of Corundum25sSelf / one party memberMitigation: 15% / 8s
Mitigation: 15% / 4s
Heal: 900 (when HP falls below 50%, or after 20s)
Aurora60sSelf / one party memberRegen: 300 / 18s (1800)
Camouflage90sSelfMitigation: 10% / 20s
Parry: +50% / 20s
Great Nebula120sSelfMitigation: 40% / 15s
Max HP up: 20% / 15s
Heal: 20% of max HP / 15s