As far as I'm aware, all of the SRAM road groups are compatible. I believe the road shifters also work with the 10 speed MTB stuff, so that may be another option.
As far as durability, stick with the power glide cassettes, not the open ones with the "missing" teeth. From what I understand the open cassettes offer more opportunity for mud to get into the gaps between teeth. I've never had an issue with chains or clogging on my SRAM stuff racing, or riding out on the local mountain bike trails.
This stuff is all compatible for 10 speed. For 9 speed mountain bike components, the derailleurs were not compatible with 10 speed road shifters.
You should be able to run an Apex rear derailleur fine with Rival shifters, and a Wi Fli 11-32 rear cassette for some low gearing. An 11-34 from SRAM/Shimano may work as well.
Regarding mud, I think there is a big difference between 8 and 10 speeds...but not so much between one gear. What matters more is the shifter, I think. SRAM's one lever makes for interesting shift results when it's super muddy because if it doesn't get there or skips, you don't have an opposing lever to play with and there's more opportunity to go the wrong way if that makes sense.
I have a cross bike with a mostly Force group (Rival crankset since that's the only one they make in 180mm), and I replaced the rear Force with an Apex this year, so I could toss a 32t cog on my all around wheels for climbing steep gravel roads in the off season.
The shifters work great, I can barely tell the difference in shift responsiveness between the Force and Apex. About the only thing I noticed is when taking the rear wheel off and on, the mid-cage length is noticeable and the chain seems to have more slack when removing a wheel.