Just loaded up the game for the first time in months and there's a 17GB update. I think I've been away too long
Haven't even looked at any DLC yet.
Yeah mate, you have some catching up to do.. I downloaded that patch a whole 3 days ago!

Seriously though, you'll be up to speed in a couple days max. Other than the House of Wolves story, you can pretty much ignore the rest of that DLC. It was good fun at the time but you're not missing out on anything. Trials of Osiris was where the real game was at but that'll be back again soon.