Tank Stances.

[Zojha]

I think having frequent mini tank busters and possibly a bit of rng element involved might incentivize the use of tank stance.

Doubtful, because tank stance only really becomes relevant in terms of mitigation when the damage is so high it would otherwise one-shot you. When that isn't the case, healers can pick up the slack easily. Heck, A12S has been solo healed with a monk tanking one of the general adds - and that was BEFORE echo.

It's a different case if healers could go OOM from healing a tank that doesn't mitigate properly or couldn't keep up with the damage. But they can overpower most damage easily and for long periods, which makes more mitigation somewhat pointless.