Mainly Poppy and Heimerdinger.
Most of the teams played the entirety of worlds woukd have been easily countered by a poppy support and/or a heimer botlane.
We only saw one game of Poppy support and she dominated the game. A couple other poppy games that kind of spiraled out of control, admittedly enough. We only saw one (maybe two) games of heimer.
I dont understand why teams didnt play them.
Thinking about it now, 
W would have gotten so much value vs literally all 3 FPX comps in the finals.
I was talking about that with a few folks after the finals. Basically Poppy was the most talked about, especially in the amount of engage comps that conspired in several games. That and I know I'm a fan of competitive Poppy cause I really feel like the W buffs really upped her value
You have to be good at those characters which is why they didn't get played much. There was a lot of room for different compositions this year but most of these teams are basically comprised of young one tricks who can play like 2 other characters barely at an acceptable level for worlds. FPX targeted Jankos with this and used G2's reluctance to ban out Tian's picks because their character pools overlap to gain an advantage by just picking Tian's character early. FPX won every draft by focusing on jungle mid pressure spreading to the rest of the map. G2 lost every draft by trying to show off and look clever.
