Are you assuming they buffed her since the mei meta seems unchanged to me. Have you been fighting the same people before and after 3.0? If you are comparing players via arena, you do know that people won't stop getting more power and initiative. You could make a case if you were fighting someone having a lower power and initiative but it would mean you might not have a good counter to that team in the first place.

Provide what team you normally used in 3.0 and in 4.0 would help out if there was something wrong. It could also be the opponent has more initiative than you so mei's barrier would be able to stay, meaning it buffs tenten and mei.