TBH I have been playing Petal in 5v5 to see if she really so bad and I sort of discovered some stuff…
Petal is actually a really amazing counter pick against some heroes. I have been having a very high winrate with her in 5v5 recently, and as a counter pick, she serves her purpose really well. Even with stronger healing in update 3.2, she will serve her purpose even better.
For example, when there are many melee heroes who are pretty bad against kiting heroes such as Petal on the enemy team, picking petal can be the saving grace of your entire team.
An actual example was when the enemy team had Skye, Rona, Reim, Foretress, and Kestrel.
Petal counters about 3-4 of those heroes and because of it I wrecked the enemy.
Also Petal is really good as an annoyer to the enemy that stops them from getting farm. Her clear speed is very fast in the Jungle and Her ganking potential with the help of her captain(like Catherine is a good pair). She counters a fair amount of the meta heroes too, such as Rona, Kestrel, Celeste in the early game, Catherine, etc.
Her ultimate in the late makes such a difference in teamfights that it quite surprising how much damage it can actually do and how much healing it can do to the whole team.
She will be viable next update as a good counter pick.
WP Petal only works against comps that aren’t strong in the early game. She really shines late game but is very bad in the early game and not much better at mid game. However it is still viable and is purely situational.