Re-binds and controller support will come in at some point, because I realize people like to customize their buttons, they aren't very high on priority.
Jump is on "w" because "w" is "up". If you wish to go up, you press up. The idea is to not require complex hand position on the keyboard, and since "space" is for dash, and that's a lot more frequent, jump makes sense on W more than any other odd key. Mouse only has two buttons, and they are used for the 2 attacks.
On a controller, there's 4 easily accessible buttons on the sides and... yes, jump would most likely be on Left shoulder button (and dash on trigger), leaving the two attacks on the right. As the game is currently, using a twin-stick control scheme, it would be clunky and impractical to use face buttons such as A to jump, because that requires you to stop aiming to jump, and that's uncomfortable in the thick of combat.
It's worth mentioning that I'm not satisfied with the flow of combat as it is. The second stick may not be such a good idea after all, and if that goes away, than controls would shift to using two-handed keyboard rather than mouse and keyboard. I would probably still use "up" as the jump button (or "w" in the WASD scheme).
Another worthy mention is that the basic Jump may not even survive development. with the Dash being so much faster and versatile, it does beg the question of whether a default jump is needed at all. More testing and more work is needed, but I figured I'd share the thought process fully.
Thanks for the feedback, cheers! =D