Has anyone with 99 wc frequently use a beaver while cutting yews/mages? I'm curious to know if they make a small difference or not.

Well I have 96 wc...I don't notice a difference on yews with a beaver *at all*. I imagine it's the same way on mages since those are higher level trees.

I used a beaver when I was getting 99 woodcutting. 2 levels is not a very significant boost, but it certainly couldn't hurt if you're already near an obelisk, seeing as it is free after all. But it doesn't really have a long enough timer to make a big profit from its foraging, maybe a few k at the most, so if you have a decent summoning level you'd be better off using a more profitable forager, like a fruit bat.