I dont think they stack and if they dont i would go with the permanent speed increase rather than the proc. right now im using mending on my weapon just because i had it availabe for free and the healing adds up decently which can help your healer out alot
Using Mending for now since neither Windwalk nor Lavawalker are affortable due to the lack of Maelstroem crystals. There's no disarming bossfight mechanic right now so weapon chains are only interesting for trash. Paladins should go with Mastery boot enchant since they don't need the runspeed.
Mending is not much healing after all, not even half of my lifebar over the course of a 6+ minute fight so i while swap as soon as it's possible and give Windwalk a try.