Please list all of your system specs to include CPU, motherboard, and PSU.

You are bottlenecking those GPU's.  You need to throw a slight OC on the Cpu and it will make a HUGE difference
 
When you are outside in larger areas in a game, that is where your CPU really gets pushed

Jmike, arguably, i think you would need a 3rd 980 and go 3x 980 SLI to maintain a higher FPS. If these mods in Crysis 2 are "HD mods", then you need more juice. CPU is one thing, but if you see that you're not bottlenecking on your CPU, then it is definately the GPUs, which can happen. And yes, you can suck the juice out of those 980's fairly quickly. 3440x1440 is a pretty high res, and by adding HD textures you know you're going to use the resources in the 980s really fast, even at SLI.
 
One way to test if you are "bottlenecking" the GPUs is to turn off those mods and run another test. If you get steady frames, then 2 things... 1) either those mods are flawed, or you need more juice within your video cards. Another way you can test if it's your cpu, lower the resolution to 1920x1080 or lower, and run the test again. If your frame rate improves, it's the GPUs that are bottlenecking with a higher resolution and HD mods added.
 
 
If anyone has any objections, please forwards some benchmarks to give a better idea that it would be his CPU. I'm only saying what i'm saying only because i'm comparing this to having HD mods with Skyrim (though i don't know if that would be a good idea to compare Skyrim mods with Crysis mods. Different game engine after all.) I'm only theorizing the comparison of Skyrim HD mods with Crysis HD mods.

Other thoughts : More than likely you are using up the amount of VRAM on the 980's

Thanks for the info Stalin, just for comparison since you are familiar with Skyrim modding,  I have a ridiculously modded install(my texture folder alone is 64gb) with 114 esps. I can put my PC on it's knees with a RealvisionENB preset with max settings but with a typical preset I get between 75-90 fps standing atop the steps in Dragonsreach or right at 80 hanging out in a heavily modded Solitude Docks.
 
I did load up my 4.6 OC and saw no noteworthy changes to Heaven/Vally and it also didn't do anything to Crysis 2.
 
I don't really have any issues outside of Crysis 2 and it very well could be the mod combination. I don't think it's the MaldoHD mod alone because that is mainly HD textures+.cfg optimizations+SweetFX and VRAM usage never exceeds above 3.1 and mostly stays just under 3. Incorporated in that is another mod called Blackfire which is a combination of Crysis 2 qualtiy mod and Blackfire's own tweaks, both of which HEAVILY alter the lighting in the game, add DoF effects, heavier motion blur. Unfortunately I cannot find the config files that control those tweaks to disable them for testing.

I mainly posted my benches out of curiosity. Like all of us, I'd like to see how my numbers stack up, but there's not much to compare it to. The only thing I could come up with is to hope I come somewhere in the middle between 2560x1440 and 3840x2160

When I get home I'll test that the best I can. From what I understand the mods slightly embed themselves into the game so it's not as simple as removing them from the mods folder, and I'm an idiot for not making a game back up prior to installing. There are several hot keys in the game to increase/decrease the strengths of many post processing effects and while I was having my morning coffee I was desperately combing through the mod files to find where those settings are stored in an attempt to completely disable them.
 
What I may do if all else fails is delete the mod folder, game exe, etc and let Origin rebuild the install, back that up and go from there. That way I can get a good baseline unmodded vs modded.