Issue: Tournament Defense scoring is not gradual enough. Though the segmentation based on win percentage looks fine at first glance, the daily cutting-off points introduce a huge variance into the score and the fact that grading does not take into account the number of attacks the team received is a problem when there is no guarantee that each team will be tested equally.
Imagine the simplest scenario where 2 players with the same defense team setup get attacked each only once Day 1 and never again. One of the defense teams is victorious, the other loses. This will mean a total point difference of 2800 at the end of day 5, a huge amount caused by merciless rng.
Now imagine that in the above scenario both of them get attacked once again on Day 5, with reversed results (meaning they both end up 1-1). Their team composition is the same, their overall performance is the same, still there will be a 2100 point difference in their scores because of the daily measuring system. I do not think this is acceptable.
Suggestion: introduce a new point system that does not penalize a player for things outside of their control (e.g. getting attacked only once and losing means E rating forever) and ensures that players with the same overall performance receive the same number points (e.g. no more carrying over previous results to determine the daily score).
One possible solution would be the following simple system: each player starts each day at 550 points, each win adds 50, each loss subtracts 50, minimum and maximum values of 200 and 900 can still apply (and of course point values can be adjusted so end results resemble current distribution more appropriately). This results in gradual scores while solving both of the main issues described before.
There are of course other possible avenues to explore, the above is looking for a solution while assuming that defense scoring and random matchmaking will remain in place.