Is weapon skillup based on how many swings you make in a minute? So hasted would result in more weapon skillups? Or is it more like a proc, where weapon delay/haste doesn't matter?
Yeah, more likely to proc per swing at a higher delay, less likely per swing at lower. As I understood weapon skillup it's on a per swing basis.
I think, and I may be mistaken, that weapon procs are just ppm based, meaning that slowed or hasted you still would proc the same overall amount of times per minute, before any riposte. So swinging at a single targets back with 100% haste or 75% slow is still going to proc the same amount of times. Where slowing comes into play is with Earthshaker, you are slowed but you riposte 1000+ attacks with the same proc rate per swing as any other slowed character.
you don't use riptose disc when shakerpaging, you use rampage aa which is an AE attack. slowing increases proc chance because proc chance is based on weapon delay, hence the Earthshaker already has a base 70 delay. as for OP's question, weapon skillup is a per swing base so faster attacks = higher chance to gain a skillup