Aw no cross platform (guess I might understand their reason, but maybe limit it to PvP?).
But my concerns about this being designed for MP/co-op first & foremost I think are accurate. I don't think this game will be as enjoyable unless you play with at least one other person during missions. Well that's my opinion anyway.
Well this being very MMO like, it not really that surprising that it feels that way heh.