You can get the same EHP as sacrier as a feca or panda but you will still be worse at tanking.
What makes resistance so much better than plain HP is that your shields migate more dmg and you need to get healed less for the same effective dmg you took.
Let a 40k HP sacrier with shitty resistance take a massiv hit, who is going to heal you up again? the 3 enis in your grp? Also whats bad about HP as EHP is that we have heal resistance.
So every point of dmg you can migate through other mechanics like shields is more effective the longer the fight will go.
Feca with 2k shield (Which is around 1600% damage, Lol at the tank that has that) = mitigated at 87% resist = 15kEHP
Sacrier 25k HP = 300 coagulation = 4500 at 75% resist =18kEHP . Still mitigates more.
There is no doubt in the world that Sacrier is the best damage absorber in the game bar Feca's PA/Immunity then again you could still argue. Colonnades's armor output.
Simply put, majority of the game bandwagoned and you rarely see anyone else try anything other than Feca for tank, Eni for healer and Rogue/Cra for primary damage dealer. You pigeonhole yourself into one set gameplay and you rarely see options outside the box.
Getting a 4k shield on a feca doenst equal a 4k shield on a sacrier. Healing a sacrier for 4k doenst equal healing a feca for 4k. You need alot more ap from your healer/supporter as sacrier.