I just played the only way to earn orbs for that triumph and it's near impossible to stay alive long enough to get headshots with the grenade spamming going on. Bungie closed down the other options to get them in order to fix the guitar bugs. So you cannot earn them in Gambit, you have to earn them in Quickplay Crucible. Bungie, give us the triumph you locked everyone except the 1% out off. Or give us back the Gambit way to earn them! Upvote if you agree plz! Ps: don't get me wrong i will grind it, but they made it near impossible to get for the average player.
The team is looking at options on this. One suggestion that we've seen is reducing the amount of orbs required for the triumph. When we have info, we'll let you know.