Small skill binding problem

Make that 7 years.

Edit: interestingly, I was not having a problem with this until today. I was able to retain my allocated left-click skill when switching back to my primary setup from my secondary one for the last few weeks, but now I'm back to weapon attack being my left-click when I go back to my primary setup.

Absolutely HORRIBLE for spellcasters. What is going on here?!

Try disable "Auto-equip" in the UI settings. This solved it for me. :)

I've had the same problem when switching between weapon sets: On each switch the left-click slot got reset. Died a couple of times because of it. Seems like the logic is the same as when picking up new weapons. Maybe it's implemented as "drop weapon" followed by a "pickup weapon". Anyway, that's how I got the idea.