Simply removing criterion dungeons instead of balancing the few jobs that need adjustments for it is a poor idea imo. People have been begging for small scale hard content, and it'll definitely be more casual than 8 man raids, but the answer isn't to delete it if two or three jobs have trouble, just to balance for it instead.

The answer could also be non obvious. Perhaps throughout certain parts of a criterion, certain parts of the dungeon experience are more streamlined. Perhaps AOE dps is more important in certain sections than single target performance is, and ranged dps could simply be better at this than what's available to most melee dps. Perhaps black mage is stronger than Red Mage at single target, but weaker at AOE. The balance team could be crafty about how to deal with that while keeping raid balance intact.

However, specifically in the case of Trick, more frequent buffs is proportional to more party reliance, as we've determined time and time again on this thread. Bringing the party buff alignment up to speed with every other melee makes the melee role easier to balance within itself, no doubt.

I'd also like to point out that people online who voice their opinions the most are more than likely the people who do not like the changes, especially before they've played it. People who like the change are more likely to determine they've liked it after having played Ninja, which is why you're probably not seeing as many posts compared to the more fervent reaction to "We're making mug a party buff and removing it from Trick!" IMO, to make a balance decision before we've got our hands on the changes is silly, especially if they feel like they've got a good reason for this. I don't feel like it'll change how ninja plays much regarding the rotation other than a shift in ogcd placement (and mug isn't a very powerful ogcd anyway aside from ninki gain) because aside from TCJ and Phantom Kamaitachi, Ninja is all about bursting every 1 min and we still have that with 6.1 Trick. But we'll see. Regardless of whether the change is good or not for gameplay feel, paired with the right potency changes I definitely see it as a buff in 4 man and solo content for Ninja right now.