In normal game play, by myself as a single player, my connection is usually great.
But, almost every time I try to play in a fire team, Crucible, or Iron Banner, I get a red bar and can barely play.
Today, I tried to get into IB, but couldn't get into a single game.
I kept getting the 'Contacting Destiny Servers' on the bottom of my screen, then my connection was lost, with various error messages.
I stopped trying IB, and just went to doing missions in the Plaguelands. (Without a single error message.)
Please stop posting your typical, useless, canned answers and work on fixing your issues!
One cause that SOME people share with your reported issue is:
Having really really low UPstream bandwidth
Like 30 down, 1 up. That if it was too low, it would cr@p out trying to connect to the 11 other people in a Crucible match but would be fine on Strikes and stuff.
Obviously this isn't the "only" answer but it's an easy one to test. What's your upstream