The game definately plays better for me in the so called " off peak " times, I find that before 6 pm UK time the game is a lot smoother.
Example today at around 4pm I played 3-4 quick games and had no problems but I tried to play tonight after 7 pm and the game was a mess, lag, 2-3 bar players, hitmarkers instead of kills etc.
The worse thing about it was I had gone back to using the Fal and I couldn't even get a second shot off, it seemed that the gun wouldn't fire and just kept jamming, I know that probably wasn't the case but that's what it felt like.
So I turned the game off and played Borderlands 2 for a bit and tried again at about 9.30 and the game was running fine again.
Do the sums UK time is about 4-5 hours ahead of the US, so by the time I start playing around 7-8 pm half of the kids in the US are just finishing school and get home and play BO2 so they flood the game and screw the matchmaking for a while.
I do agree with you about the lag comp, it's very easy to blame that for most things but when I notice a bit of lag I just stop playing for a bit it's less stressful that way.