I've never met anyone whom I suspect of cheating, but I imagine I'd finish the game and then report it to an admin.
Facts
How do you know they are cheating?
I bet of the 200 to 300 people you have blocked, less than 10 percent of those were actual cheaters. You are paranoid. Your stats show you have played about 2000 blitz games, which would mean you suspect 1 out of every 6 to 10 players as a cheater.
"when its obvious the other guy is using an engine"
Translation: When I lose.
he thinks he is perfect. it is that simple
I've never met anyone whom I suspect of cheating, but I imagine I'd finish the game and then report it to an admin.