New Resolve Keystone which could help tanks

Vanguard (not sure of a good name)

Entering combat generates one stack every second for the next 3 seconds. After reaching 4 stacks, your next basic attack against an enemy champion consumes all stacks to grant 6 - 35 (based on level) bonus Armor and Magic resist for 3 seconds and reduces 20% of true damage taken from champions to for the duration. All stacks will wear off after 3 seconds out of combat.

Melee champions refresh the bonus reduction duration when going in combat by affecting enemy champions.