Same here. After 5.4 patch only in SoO progress raids almost every raid WoW freezes once in 2hrs raid. Normal mode 25men.
PC is i3-3440, radeon 7770 and Win7 64bit fresh install few months before 5.4 patch. I will try to run in DX9 next few raids and see what will happen.
Edit: I have 13.4 catalyst installed. Can upgrade those to 13.9 WHQL if I remember correct.