Seasonal boosts are actually very good game design
It seems like the general consensus on here is that the seasonal boosts are bad for the game, but I couldn't disagree more.
This post recently reached the top of this subreddit: https://www.reddit.com/r/marvelrivals/comments/1haoq4j/seasonal_boosts_need_to_be_removed_to_preserve/
and honestly I think all the points they make are pretty much exactly WHY the boosts are good. Games are most fun when the meta is being figured out and things are fresh. Saying that the buffs "makes it impossible for the community to correctly ask for buffs and nerfs" is just complaining that the meta wont be completely solved this season.
I understand some of the complaints about the passive buffs being overtuned (mostly hawkeye/hela), but changing it to be only active with the team-up would be terrible. The reality of any hero shooter is that team comp is the highest cause of friction in the game and passively incentivizing the linking characters to be picked relieves at least SOME of that.
In the end the actual abilities and buffs they had in season 0 could be massively improved, but the overall design of the system is good and doesn't deserve all the criticism I see on here.