I've been putting hours upon hours into Syndicate lately, gearing up for our review which will go live tomorrow. Along side the single player, I played a ton of the game's co-op campaign this weekend on the Xbox 360, but ran into a few issues I thought I'd give people a heads up on before the review.
As of now, you can't play the game in co-op while in a party. Why? Well it causes the game to hard lock or refuses to connect to other players. It's a known issue, apparently, and it's something that should be rectified eventually. It's just not entirely obvious when it happens that this is what's causing it. From what I can tell this issue doesn't exactly affect PS3 or PC players.
In my half a dozen sessions with players almost everyone experienced a lock up at some point - mostly it occured when the team lost mid-mission and the game went to reload from a check point. At that point the host would lock up and everyone would drop to the menu.
Moral of the story? Don't lose.
Our review of Syndicate goes live tomorrow, 2.28.2012.