The main reason for the no-duplicate-characters-rule is to give teams some more variety other than top-tier-exclusivity and to give players who don't use top-tier characters a chance to do some damage.
It doesn't encourage diversity, it forces it...but it actually doesn't. Those 6 Ciel users are still going to enter, just on different teams. Potentially there are more Ciel vs Ciel games if they are spread out(I think, too lazy for math). Unless there is some really broken character(which there isn't in most games) same character teams aren't ideal. Theres no reason to take a mid tier player and hope they do damage if you can take a high tier player that probably will do damage. Forcing two top tiers to take a mid isn't diversity, it's forcing everyone to watch a game that should be for 8th place but it's in the finals. If the mid can actually win against a real team member(not just the other team's mid), then the game is balanced enough that the rule isn't helping anyway.
I guess I'll have to settle for Ciel/Sion/Len Ciel/Sion/Warc Ciel/Sion/Miyako Ciel/Sion/Akiha Ciel/Len/Warc Ciel/Len/Miyako Ciel/Len/Akiha Ciel/Warc/Miyako Ciel/Warc/Akiha or Ciel/Miyako/Akiha for team players who don't use top-tier characters still don't have a chance to do some damage. It's no different than just banning a character you don't like. Instead of a being the best, it's now b, or in this case instead of aaa it's abc. The only problem with this is if aaa is actually the best, then either it's by such a small margin that it being the best is very questionable, or character a needs to be banned.
Adding an unnecessary restriction at this time is, as chibi so precisely describes the rule, "fucking stupid". It's a fucking stupid restriction at a fucking stupid time.
