I don’t know about anyone else, but part of the reason I find the arena boring after a while has little to do with trophies, and nearly everything to do with the arena itself. When you reach a certain point in the game (for me it was Badlands), you’re going to be stuck at that point for a long, long time. During this time, you’re going to see the same arena over and over again.
Suggestion - once you unlock an arena, allow us to choose between all unlocked arenas. We’ve seen that these are merely backgrounds anyway via friendlies. It just breaks that monotony of fighting in the same place.
The arena exclusive DNA would still be there, it’s just that it would be based purely on trophy count rather than arena (alternatively, even better - keep it the way it is now and allow us to decide what we want to farm by selecting said arena).