Udinese?!? Arsenal and Man City are going to have tasty opposition. Arsenal can't get Dortmund, Chelsea or Man U and Man City can't get Bayern, Chelsea or Man U. Remaining 5 teams they can draw are: Atletico, Real, Barca, PSG or the Bayern / Dortmund. No easy game there.
Yes, had Dortmund not scored the winner to win their group then Arsenal would have topped the group with Udinese in 2nd. That would mean Udinese were an extra option for Man U and Chelsea, hence those two sides being quite happy Dortmund took the group.