Sheltron generally blocks ~20% of damage taken, an additional on demand 20% damage reduction from all tank busters/aoes/whathaveyou is about the furthest from useless I've ever seen.

Picture this: would you rather you need to choose between mitigation and damage from your gauge, or would you rather be able to switch (relatively) freely betwen stances, and have your damage balanced around constant, high dps?

It doesn't make sense for those that call for offensive use of gauge when we already have a much better offensive toolkit than we did, as well as unbelievable party utility with intervention, all our CDs, path of shininess, clemency burst healing better than healers, etc etc.