is not a bad champ at the moment. He isn't amazing, but I think he is in a good spot. Skarner is just not very riveting to look at and play for most people. I personally enjoy playing him but few other people do. Skarner used to be about the same before his rework, besides the spires. Skarner's old passive was Crystal Venom and allowed him to autoattack a champion that had 3 crystal venom stack on them to stun them. Skarner's abilities applied crystal venom so he would have to fight for about 2-3 second before he could get a stun off. Now this passive was moved to his E where he can instantly get a stun off if he lands it when he autos the champion hit. He had cdr for all his abilities when auto attacking rather than on just his Q. His W is basically the same as it was before but now is max HP scaling. And his ult is about the same as well but has Base AD scaling to incentivize him to build more AD items.
Skarner's damage is not that bad, just he needs to be in his spires to fight. Before all of his nerfs it would be impossible to duel him in his spires and he cleared the jungle very fast. You can't really have a stat check tanky duelist who has 2 forms of hard CC in the game and have it turn out well.