Oh, yeah, that makes it totally fair.
Well, more seriously, Player vs Mob mechanics have several significant differences.
Saying its not fair is saying its not 'baransed' ..
Pld can get the same level of damage reduction, but you need relic/empyrean iirc.
Also, bst main can actually get up to 62.5% damage reduction using gausape and killer effects.
but really, its the end-use of these abilities which would make it fair or not. On the outside, 50% vs 87.5% sounds like a huge disparity. but Players have much more curing and other tools available compared to pets. Comparing the damage mitigation caps alone doesn't really compare the balance.