[hi19hi19]

Zyra is very powerful in OFL, I think. She is fairly strong and safe in lane, has the range and self-peel to be played AD, she can jungle, she has the utility to support, and her AP build paths have a good variety from full glass cannon DFG to tanky with Liandry/Rylai and resist AP items.
Also a team of Zyras can take Baron when it spawns in like 5 seconds, so that's cool.

From what I can tell, the lane-dominant ranged AP carries are the strongest. Annie, Zyra, Nidalee, Kennen, etc.
Depending on who it is you either just stack AoE ults or splitpush/siege endlessly and win.
AD carries are strong too, especially Ezreal and Caitlyn, but they are a little less varied in how you can build them.

Melees are fun but all-melee teams have a hard time pushing.