Petra is the worst map ever made for Overwatch.
Its verticality means you either pick one of a small pool of heroes that can scale walls, jump or fly, or you will spend most of the time running around corridors trying to find good angles and positioning for your character, just to get one-shot on the way there or overwhelmed by multiple enemies and then having to start over.
If it then spawns you in the lower corner where you have really only one way to go up, you’re screwed.
Please just add more ways to reach highground for characters.