3D Graphics Support on a Radeon 6870 for steam gaming

I'm running Arch Linux and I'm trying to get a Radeon HD 6870 setup for gaming on Steam, specifically for Windows games such as Skyrim and Dark Souls 3 using Wine. I've done this on a desktop with identical hardware, but an nVidia card, and everything runs fine. However, doing the same with the Radeon card is killing me and I cannot replace the card right now. Since I have newer hardware (Ryzen), I need the newest kernel and Xorg, so the current catalyst/fglrx drivers are not an option (as they require xorg 117 and the lts kernel, which don't have Ryzen support and has issues with Ryzen), but it seems the current mesa drivers (pulled from mesa-git) is just not sufficient using the default configuration. Does anyone have a recommended change to the PKGBUILD that would help me here? I know there are several options on the mesa-git PKGBUILD that can be tweaked. Specifically, a lot of games require OpenGL 4 it looks like when running them through Wine, and I can force the OpenGL version, since its not natively supported due to missing FP64 extensions (which aren't really used in most games), but that causes crashes in the OpenGL wine dll. Linux games seem to run fine. Any ideas?