Heres a re-cap of current ideas=
A little note: Increasing weapon damage too much may further imbalance them on other difficulties rather than balancing the game - most people do not play gold exclusively. I do think some weapons need a little boost but certainly nowhere near the magnitude some people are talking about. And its not just AR's than need the love, but all low damage high ROF weapons currently suffer the same problem, incisor, scimitar, shuriken etc, so the same fix could apply to them as well.
Reducing enemy accuracy on gold: a less invasive change that helps weapons with sustained fire get more bullets on target, It will still take longer for the average AR user to kill that enemy than the guy who can just pop out of cover with his semi auto high damage weapon though.
Aletto's idea about giving rapid firing weapons more of a damage bonus against shields is good, but I still think it needs something else too, a team using phaestons and vindicators would be screwed on those waves where you get two or three banshees and brutes respawning whilst you are trying to cap an objective.
On another note - its not just about making the guns "viable" on gold, its making them so people have a good reason to use them on gold, because if you don't put them in a situation where the gun works better for them, they will all still just pick the same old gold weapons they always have.
Embellishing on the boost against shields idea, adding a threshold where any shots that do above a certain damage get a percentage based damage reduction to the shield mechanics would make it so low bullet damage, high ROF weapons are much more effective against shields. Sort of the reverse to the armour reduction where low damage guns get more of a penalty. It could fit with the lore well too, and be explained that higher velocity shots and larger slugs encounter more resistance when entering shields - like in the original Dune movie when Gurney Hallek is teaching Paul that a slow blade penetrates the shield, but a fast one does not.
Another idea I have seen around is the idea of adding a mechanic where the more bullets hitting a target in a short space of time, the more of a chance of the enemy flinching - sort of a suppressive fire mechanic. i think this would fit very well with the point of the enemy accuracy decrease idea - the enemies you shoot would be much less likely to shoot back. Albeit only the ones with no shield s or armour, but it adds to the general usefulness on all difficulties.
I think increasing the clip size and fire rate of most full auto AR's(and other rapid fire low damage weapons like the incisor and scimitar etc) rather than the damage would keep them more fitting to their original roles, and this coupled with the new shield damage idea would work well.
I know my idea for waves of high quantity, low health enemies (page 4 if you want to read it) sounds overly complicated, but the premise is simple - it does not have to be delivered in the way I described it. Enemies could have grenade usage reduced, and any kind of wave works as long as there are lots of low health enemies. My idea is not necessary at all if the other changes that we have come up with are all applied, I was mainly partial to my idea because it also balanced power usage by making some underused powers better choices, as well as certain class powers like Ad rush, sentry turret etc and as such wouldn't just increase weapon variety but class diversity. I understand it sounds a bit over the top, but I would like some new types of waves to be added to the game anyway for fun so I thought of a way the ideas could all go hand in hand.
I still say that enemy balance is what is mainly affecting these weapons so adversely - the increase of armoured enemies makes them much less effective, whilst the increased health makes it so you have to stay out of cover for longer, and their current advantage over the shield gate mechanic is pitiful compared to say the advantage high damage weapons get against armour comparatively.
Increasing the minimum bullet damage against armour on gold from 5 to 15 would instantly make the weaker assault rifles a lot more usable - I think the Revenant X currently does approx 9.6 damage per bullet against armour with no mods at a fire rate of 650rpm or 104DPS, to give you an idea. The gun is regarded as barely useable on gold, nothing special. A predator X bullet against armour does 23.5 damage, at a maximum fire rate of 500 RPM, now I know that is not going to be reached as it is semi auto, but a typical person shooting it can easily hit 5 bullets a sec which is 117.5DPS, has perfect accuracy, and can pop in and out of cover between shots if needed. The Revenant will likely miss quite a few of those shots due to accuracy over range. The Carnifex does 294 damage per shot against armour - thats 490 DPS. Increasing the minimum damage to 15 would make the revenant do 162DPS, around where I think it needs to be. If this was implemented the new DPS for assault rifles against armour would be:
Assault rifles VS armour on Gold.
Avenger Original DPS:41.6 New DPS: 125
Revenant Original DPS: 104 New DPS:162
Phaeston Original DPS: 50 New DPS: 150
Geth pulse rifle Original DPS:75 New DPS: 225 - (when I worked this out at first I thought this was a huge flaw in my idea, but then I figured, why not? The gun doesn't really have any great use or purpose other than its accuracy, if it ends up being the best all-around full auto against armour that's a niche I can actually appreciate)
Collector assault rifle original DPS:45 New DPS: 125
Vindicator 3 shot burst: 107.4 damage (ROF is around a burst and a half per second, so around 160 DPS vs armour) - the vindicator isn't affected by my change by the way, I just thought I would include it to show a comparison.
The mattock is semi auto and fire rate depends on you, it does 45.2 damage vs armour per shot, so four or five shots a second and you are looking at a similar score to the geth Pulse Rifle.
I havent a clue about the Harrier. The saber, striker and falcon I leave out because this wouldn't affect those anyway.
What does anyone else think? They would suck much less against armour. More of a change or less of a change? I felt that more would too heavily affect the GPR's DPS, as it has a ROF of 900, hence the huge change by altering 5 to 15.
Ideas? Sorry for the wall of text..