TOP cleared with no healers

[Semirhage]

And now Ultimates, the penultimate combat content in this game

(tiiiiiiny grammatical correction: penultimate means "second to last".)

Why is only one role of the trinity in a trinity game being treated as expendable? The fact that it's only very skilled players that can pull this off is irrelevant, the problem is that it's even possible to drop one of the trinity in a trinity game, in the hardest content in the game too.

Oh that's easy. This game is designed by people who main DPS classes and it shows. There's an occasional tank voice in there, but otherwise the tank and healer legs of that trinity stool are seen as something that exists to prop up "my" fun, not something to be fun or useful by themselves.