Well, he plays with between 100 and 300ms latency on average, atleast whenever I check the player screen. They're perfectly capable of hitting targets reliably.

On a similar note, I used to play World of Tanks with around 400ms latency before I got a better internet uplink, while it's certainly bad for a month, you start to get used to it eventually and the brain compensates. Of course, if reaction time matters you loose, but you can adapt your playstyle in a lot of games so that pure reaction time doesn't matter as much.