Did you ever get to the bottom of this @heretolearn ? I have the same problem but I'm running 3x Sapphire 280x. I believe the advice about VBE7 is the best - cards with older BIOS installed don't seem to have the same problems, as they run around 10C cooler than the same hardware with newer BIOS installed. Basically, any undervolt needs to come from the BIOS and not an application like trixx, or the cards throw a fit.

The other possibility is that the motherboard isn't delivering the right amount of power to the cards all of the time, MSI is not an expensive brand, they are a relatively young company in terms of their competition. I have been having the same issue as you, and my Asrock board is definitely a possible factor.

Does this ring true with anyone else lurking here?