First step is to switch the WoWclient to DX9 mode, and restart the WoWclient. If this repairs your issue, we are done.
If no joy, then the culprit is one of the Buddy Store products. Disabling (or not using) the product on the HBclient-side is insufficient, as products can interfere with framerates even if they are disabled. To correct the problem, we will need to disable the streaming of the products from the Buddy Store itself. This article shows you how:
Once you've isolated which product, please report the problem to the product's author. Also, please tell us which product you discovered is the problem, so we can analyze the situation and see if we can place safeguards for this in the future.