Skarner's new slow sucks and makes him more generic than he was before. Cleaning up old and antiquated kits is all well, but I utterly dislike the constant streamlining of champion mechanics. I've been playing since Beta and in my honest opinion, every single champion kit so far has something which really sets him apart from other champions - and with Skarner's new kit, I feel that part of it has gone from him. Sure, he has his hilarious Ult and autoattack-spellflinging mechanic, but now he's not even close to the kick-ass chaser he was before, efficiently hunting down enemies despite his very limited range. It's almost like a paradox - but the new kit just goes ahead and streamlines that gameplay design to a generic bruiser with a mid-range slow.
Perma-slows are a dying breed and I suppose that is for good reason, but does it really have to be killed this hard? I've thought about the slow and ms buff distribution among Skarner's current (4.2) kit and here is my proposal to 'fix' it:
This way, he keeps a potential perma-slow - but the enemy has the ability to respond to it. Also, a new movement speed mechanic similar to Vayne's passive which only works for chasing enemies to reinforce his role as a chaser. His Q and ult would stay the way they are now. The slow and movement speed values are probably a bit off. But you get the idea.
For reference, here are his pre-4.2 Q and W which used to house Skarner's perma-slow and movement speed buff, respectively.