What do you mean on 6 total people?
Unstable light can only debuff someone standing in the Light Pools. So if you have 2 Gazers, they'll never see the debuff.
You're going through six pools, you'll have three people doing DPS as you need two gazers and one person managing adds. That means you'll lose a lot of dps because someone will have to get out of the pool six times (one time for each pool), leaving you with two people doing damage on golgoroth for that time. It seems like the encounter will be a lot longer now with so many fewer people doing damage on the boss, which means the fire team has to be a lot more consistent about staying alive, dropping the next orb on time, getting clear of everyone if you have the debuff, and etc.
I worded my previous post poorly.
On second thought, though, the damage buff lasts a few seconds out of the pool and you can damage G with unstable light, so I suppose that makes up for it.