The best way to address this is to have Tenacity replace Strength as a new primary stat for tanks. Tenacity is always going to be kept tightly in check as long as it's a secondary stat to prevent there from being large disparities in tankiness. But all those features - damage output, mitigation, and healing/shielding received - should continuously scale with higher item levels.

In return, make Direct Hit into a tank secondary, and encourage players to maintain a balanced portfolio of Crit, Direct Hit, Determination, and Haste, without making one or two of them clearly the best and encouraging everyone to double down on them.