Well we could have an extra arena where we try lots of different stuff. For example a slightly different change in balance and then we notice which arena people like more.
If we have let's say a return / tidal free arena for a week and the majority prefer to play there instead of the normal arena, then something might be seriously wrong with return. I suggested this before, but i think their fear of return actually being overpowered prevented it from happening, since then they would have to nerf it without hesitation.

