i have now one games as mid, jungle, and support skarner.
Support Skarner is actually decent. Maxing E give a lot of poke damage and a lot of slow, and the ult is just hilarious as usual
Mid works as well. I basically do the same thing as I do with support, but then with the AP I can do a lot of damage with ult and ignite and q and E, and I can land the combo even if opposing mid is Kass, which he was.