The problem with this is melee are still going to stick to you and slow you by 50% forever.
Im all for more movement, but PvP won’t change much.
Reducing Melee gap closing potential would help, but then they would be gimped. Best thing I would suggest is remove the spell push back. Or give range players like 5yards extra range and see what happens. I would suggest 10 yards more, but then that would making the kiting potential worse for melee.
Another option is to just increase the CD of gap closers in PvP but also reduce the effects/duration/CD of CC in general.
PvE is a bit harder, because if I remember correctly classes like Warlock had an entire row to mobile casting in MoP and many other classes had some movement (Shaman could cast the filler Lightning Bolt on the move).
I 100% believe they should go back to a casting on the move model but limit it to specific spells or have a drawback (like 30% longer to cast or something, even 50).