For those having issues with channelling skills (like me!) after the recent patch, it turns out that setting the first slot - typically Q for PC, allows the skill to function normally. Massive credit to those who discovered this and worked to disseminate that information.
If you’d rather use the normal key or mouse button for your channeling skill, you can rebind skill slot 1 to your preferred key/button and then set Q as the key for the other slot. In my case, I had Warpath bound to RMB, so holding down Q when I wanted to also use other skills was annoying. So I changed skill slot 1 to RMB, and the original RMB skill slot to use Q.
(Now for being able to use 2 channeling skills on the same build…)