Morde's great in ranked, he's a counter to many and extremely hard to counter.
His shield is anti-poke so he can just farm all day. Hes helpful in teamfights since 3 of his abilities are AoE and his ultimate can be used for him to tank or to completely wreck on a ad carry and have it help your team.
Except morde's easy to counter. Literally, level 2 gank will throw off his game so hard it's not even funny. Heck, just early poke will ruin him. You can outlane him with pretty much any AP mid so long as you start poking early.