I'm aware you can report players after the game, however I feel there must be another way of reporting players for cheatign when it become obvious. 

Is there a way to submit a player for a review outside of the game?

For example for map hacking, something i imagine without a replay with time stamps, it is impossible to even consider if it is an accurate report or not.

I've recently played again someone who, in the game it seemed fishy, and in review it become obvious (using arty on blobs out of nowhere with 0 vision for example). Even just googling his name, multiple people have alreay moaned about him. I expect withut someone literally reviewing the game in question, nothing will be done.

Please let me know if there is a process to formally report someone out side of the end game option.

Best to report using the ingame report function at the end of match screen.

That does nothing, I'm convinced of it. Otherwise this guy wouldn't still be playing