I'm on a 290x and Wattman is causing all sorts of problems.
Firstly it's incompatible with any overclocking software and will cause artifacts. I uninstalled Sapphire Trixx and uninstalled/reinstalled the driver and I still had the following issues:
Wattman will eventually for no reason lock memory speed to 150mhz.
Inputting values for voltage does nothing unless I input some ridiculously low value like 10, then it sticks, and then I can raise it up to 900 which is still much too low.
If I set fan speed to 0 (card is water cooled), the fan speed bumps back up to 1200 regardless.
Please fix Wattman. You should have the ability to DISABLE wattman now and forever! This has been an ongoing issue for quite some time now (with overdrive) and causes conflicts when using overclocking software. Please do not let wattman take over settings without us allowing it because it causes instability since it doesn't have all the ability that other overclocking software has and applies settings that are not stable!!!! add a slider to disable wattman and all of our woes will be over! But yeah also fix it!
Are you saying there is no choice as to whether you use wattman/overdrive ?
Hopefully you have reported your problem with the issue report link, so as others may not experience the issue in future.