I am a bit curious about it, i think it should be actually very good in the current meta, maybe not as good viktor and stuff like that, but still he can be an excellent pick.... but we don't see any ziggs from the entirety of S5, any thoughts on that?
He was picked because he was good at turtling in base and stalling out games / defending against sieges. With the changes to dragon and baron, he isn't as desirable. If you try to stay in base too long, the enemy just collects 5 dragons and baron and runs you over. Also, baron buff on its own makes Zigg's life hell just because of how hard it makes killing minions. A Zigg's that can't waveclear is near useless. His CC is weak so all he has to rely on is damage and zoning and there are champs that do those jobs better (Viktor, Azir) while not being completely skillshot reliant. Finally, his ult nerfs kind of sucked for him
That's all I got
I think his sieging potential is really diminished whenever he has to face someone like Azir. Since a lot of pro players favor Azir, I don't think Ziggs will be seing as much play. But Ziggs can be swapped out for Gragas when it comes to returning some of the utility back. That's just my thoughts though.
because he got nerfed to the ground. His Q hitbox got nerfed to the point where it is hard to land it. Rito doing what they do best
buffs and 
being added to the game saw the death of Ziggs pro play. Before that there just wasn't a good way to get to him while he camped you under tower. Now support/top/jungle with or just hits active and you run at him. He doesn't have a good escape plan from that. So now there are different comps build for siege that can still deal with the enemy speed boosted running at you counter strat.
i honestly have no idea, i think that´s just a thing of a champ nor being played for a while and getting forgotten. But there are so many teams currently that don´t go for solid engage and would be destroyed by a well performed poke or 1-3-1-comp (especially those siegecomps get hardcountered by the massive 1champ waveclear of ziggs). i´m also sort of depressed that noone is going for Lux, she´s insanly strong right now and there are some players in the tournament that do play her.
Because meta has shifted into flanking and hard engaging the enemies and Ziggs, Xerath and others are really weak to those. Plus the lack of items that help said champions against high hp pool champions.
