So first off, the game gets buffed by SLI and overclocking just fine.
Your CPU and RAM seem mostly fine. I completed the game in 2014 with 4 gigs of DDR2.
Your low RAM will cause stuttering because you're swapping on your SSD (hopefully you have your pagefile on the SSD and not the HDD).
If you have the thing installed on a spinning platter then I don't doubt the performance fluctuates when the engine streams content. Think about how big the game assets are and how slow an HDD is.
I hope you are aware that DSR means you're rendering the game in 4K and downscaling to your native resolution. Even SLI 980's have trouble maintaining a constant 60fps across all environments in DA:I at 4K.
Your GPU overclocks are not very significant, your cards are almost stock (for comparison, I didn't get incredibly lucky in the silicon lottery and even so, my 980's are running about +300MHz above stock).
I hope you know this, but in overclocking modern GPUs with stock cooling, you are likely to run into temperature-based throttling first and then the TDP limiter. You need to adjust your fan curve to dodge the first problem and raise your TDP limiter to dodge the second. Otherwise you will benchmark well in synthetic tests but your performance will tank in actual heavy gaming (which DA:I is). You can verify that this is the case by keeping an eye on your GPU core frequencies while gaming. If the freq is oscillating then you're most likely being throttled. If it's pegged at your core turbo frequency, then you're golden.
Observe your GPU analytics anyway while gaming in order to verify that you are in fact
1. using both cards while gaming (by looking at GPU core usage)
2. overclocking both cards (by looking at core frequencies)
3. not running out of VRAM when the framerate tanks (by looking at VRAM usage)
If you get roughly the same framerate across all the different quality settings then it's obvious you're being capped by your setup. See that you're not running with framerate targets through your overclocking suite, GPU driver, etc. Check power settings, disable frame syncing, etc. The usual suspects.
Learn the ingame settings. For example stay away from ingame MSAA. With a single 980 one can get pretty good framerates at 1080p at maxed settings, with AA off. I get your framerates on my laptop with a 980M at 1080p with maxed settings and 2x MSAA. There are countless threads on this forum about the ingame graphics settings.