Are my mitigation numbers off ?

[Reynhart]

Did we suddenly stop assuming that warriors are always your first tank

We're assuming that WAR is always the Main Tank, which is as flawed as when people tought PLD was always the main tank.
And stacking two WARs is not as bad as two PLDs or two DRKs, because you can have 100% uptime for both Storm's Path and Storm's Eye

I think you need to do 2 charts for an all physical opponent and an all magical opponent and then maybe try to get an average out of those to estimate a mixed opponent.

I can. There's still a problem.
How do I include Holmgang and Living Dead, since they're still a big part of how tanks can survive ?