USB Hub issues with Macbook Pro (retina, 15", mid 2014)

So I have a powered USB hub and I've been plagued with issues right after upgrading to the first version of Yosemite. The issue is simple: the hub has 10 ports, 4xUSB3.0 and 6xUSB2.0. I have a WD ext. HDD and usb-to-ethernet adapter connected up to the hub (both USB 3.0) and a razer mouse (USB 2.0). Every so often, usually randomly, the USB 2.0 devices connected to the hub stop working. There is no problem with the USB 3 devices, just USB 2.0 devices.

I tried upgrading the mouse firmware, restarting the machine multiple times, shutting it down completely and doing a cold boot - but nothing seems to work. I'm currently on 10.10.5 Yosemite. Please help!