Yes, that's the major reason why I try to avoid LHR T3. Check-in desks are always crowded (checked in online with Emirates last year only to get to the check-in desks to be told their Bag Drop desk wasn't open and I'd have to join the loooong queue with everyone else. I eventually found a supervisor who conceded that I could use the Business check-in desk) then you go up stairs and have to fight your way to security as the concourse is so crowded with extended families waving people off.

T5 on the other hand is (usually) a pleasure to use. T3 really need to get their act together.