In my opinion, he is extremely strong, a little bit sleeper op if I might add. He just needs some practice to do well on. He has his own niche, which is being a tanky bruiser with powerful dueling, CC, and disruption, but is mainly defined by his ultimate which has many uses and is very powerful. His only problem might be reaching his targets, but it's not that hard with his W, E, Chilling Smite, and some practice.
His clears are very good, and you don't lose much health after. Just run Full Attack Speed Marks and Quints, and watch the magic happen. For his build, get Cinderhulk, Mobis, TriForce, Frozen Heart, and Righteous Glory as core.