I would say he's around top ten. Definitely has flaws as pointed out earlier in this thread, but I am still waiting for more Erron Black players to shine. I really think Sonic could play anyone and beat most people. Keyword being most.
I hear a lot of how Marksman might be better than Outlaw. I'd personally would love to see this, so EB players, keep practicing and attend your tournies.
EB is definitely not Batgirl (I also think the whole Sonic being the only one to play BG with high success is because he put in the time and was not used as a quick "pick me up to body people in pools" character, even if she was top 2) so I would imagine more EB players could have success. He doesn't seem that difficult to play aside from some slight nuances in timing for Outlaw, and I never played a cancel character so I can't speak on Marksman.