Against Geth, actual double hits don't really matter, but since they clump you can hit more than one unit per shot.
OP could also consider Salarian Engineer spamming Energy Drain.
Ah, I didn't notice Salarian Engineer. Yeah, SE vs. Geth should be relatively straightforward on Gold even with a crappy manifest.
Alright. Yesterday I tried my own advice and solo'ed Gold against Geth on Giant. I chose the SE with Mattock similar to the build suggested by capn. The only adjustment was that I took only an AR amp II and the Thermal Clip Storage Gear to meet OPs limited manifest. My build
Lessons learned:
- Geth Scanner is a crutch and I need it!
- tried to save consumables because OP can't hold 6 missiles/ops/gels - of course got targets W3 and W10
- without enough consumables you can't: ragegel, rageops, rageTCP, ragenuke the double prime W5 and W9
- you and your decoy can RHA-tank 2 primes, but get screwed by 2 bombers
- some random quote:
The pyro...is behind you!
I'm nowhere near a solo specialist and my aim is known to be ... unreliable at best. It took me nearly an hour and I wasted 2 gels and 1 ops in W7 because derp mistake and a missile to try to switch targets during W10 (Pro Tip: does not work if you only hit primes!)
So, OP, maybe you're a real solo pro and a natural and get it done. Otherwise you may want to wait at least until you can hold all 6 consumables and probably until you have better equipment/weapons.