So for this season we will only consider players who have played in the Champion league for the majority of the season in the leaderboard rankings.

This is totally vague.

How long is majority of the season?

For example, I have been in Champions League for at least 4 days now having struggled to get there all season long despite having Lvl 6 - 8 summoners and monsters, mostly because I was being matched with maxed out decks.

Does that mean I will lose the rewards I have toiled for this season?