The indexes were by all accounts were fairly well balanced to the point that most people were happy with them. A bit of tweaking and all would have been solid.
None of those people were Tau players.
I'm reserving judgement here until we see how things lie when the DG take the field. A lot of hoopla out there about mortal wounds, but mortal wounds done in the 1s ans 2s are really not the end of the world unless you're playing a super elite force.
T5 is not what it used to be, nor are MEQ saves. The only thing so far that gives me significant pause about the Death Guard is Disgustingly Resilient, which seems very, very good. But then, that rule was in the Indexes anyway.
Of course, the fact that it seems Plague Marines are going to cost less than Rubric Marines still pisses me off to no end, but this is literally no different than any iteration of the game ever. Plague Marines have *always* been the best cult troops, and it seems they will remain so. Forever.