I think there are far more situations than you give the game credit for. If you actually think about it, this is what is currently happening:
- Mechanic that forces the melee jobs to disengage is telegraphed.
- Melee starts combo.
- Melee hits second step of combo (possible)
- Melee uses gap opener
- Mechanic goes off
- Melee uses Ranged weaponskill (combo interrupted)
- Melee uses gap closer
The interruptions are happening completely due to melee dps and tanks being greedy and trying to get in just one or two more gcds in before they move which causes the ranged weaponskill to interrupt the combo that they left incomplete. With a 3 step combo moving early would not be as much of a penalty as this becomes the "safe" strategy:
- Mechanic that forces the melee jobs to disengage is telegraphed.
- Melee uses gap opener
- Melee starts ranged combo.
- Melee hits second step of ranged combo
- Mechanic goes off
- Melee finishes ranged combo
- Melee uses gap closer
As for how to counter button bloat, 4 words: one button ranged combos.