WoW proved it was a bad idea to not design all classes to fill a role equally. If it's beneficial for DPS (or healers for that matter) to interrupt, then all classes that are supposed to fill a DPS role need to be able to do the job.
As it stands, Sage DPS has a ranged interrupt. Apparently scrappers do too. Commandos do not. It is a design mistake and will cause problems in the future.
It's not the only questionable design issue though, at least Commandos got battle rez in 1.2. We still need the Rescue ability though to have parity.
You mean WoW (and SWTOR, and Rift, and...and...and...) proved that having all classes bundled in "role" categories is a bad idea, because then you have to balance them heavily against each other.
Classes should fill different roles altogether. Pure tank, Tank damage dealers, Pure healer, Pure support/buffer (that wouldnt work well with the 4 man mechanic though), Crowd Control and utility, ranged damage, melee damage, and all the hybrids.
Then you still have the issue of balancing so that all roles are useful, but it sure as hell better than making all damage dealers do the same amount of damage and the only difference being in what order you push the buttons...