Okay so I am not against nerfing the sustain just because getting to infinite sustain or infinite blocking is not at all difficult atm. There is no need to make choices with regaurds to builds, just maximium DPS (or Heal or Blocking) all the time linear and boring really. But we will now only see better players be able to extract maxium dps and run all dps all the time without needing some sustain.
However, right now there are a bunch of vet dungeons (I haven't done other end game content), where maximium dps is the only way to defeat the boss, If players now opt for sustain they are going to seriously struggle to defeat these particular bosses. Will these bosses now be nerfed to allow lower dps, more sustain focused builds still be able to complete them?
Part of what makes this an issue is that to even get that high dps you need the monster helms (sets) which you can only get by doing this content repeatedly.