I always considered him pretty good, why did he disappear all of a sudden?

He isnt really seen in tourneys (still hoping the rest of the S2 championship might have him) but there are some high elo players that use him consistently. iKarry is good to watch.

He was in like one tourney that I saw.
They lost, but yeah... he was there.

Because without his ult he's pretty useless with long CD and low damage output

people complain about his W being a self-cc, and most think he's boring to play as.
I personally love him, and would love to see a pro play him. It's a shame Xerath is countered so easily...

it's not that he's disappeared, it's that he's never been in the competitive scene in the first place, he is an amazing champion but is harder to play than most, there are easier champs that get the job done. (not to mention he doesn't specialize as well as some other mids do, such as karthus on damage or orianna on control)