The biggest problem is that it doesn't look like Skarner (or a scorpion, for that matter) and it doesn't really feel like Skarner. It lacks a lot of his core visual elements.
Skarner has claws, legs, and a somewhat bulky frame. This new skin gave him chainsaw arms, took away his bulk, and gave him treads. He doesn't scuttle anymore - he drives.
On the positive side, the tail is a neat idea and it looks pretty good. Beyond that, it should have gone back to the drawing board.
The biggest problem is one that the OP identified - This was three years in the making. Skarner fans was desperately wanted this, especially since he had been neglected for so long. This does not look like three years' worth of work. Frankly, the 975 El Tigre Braum skin looks like it got more love than this one...