I'll put it this way: In what way will that help Larian better develop the game?
We don't have all the races in yet, we don't have profiles for all the races voted on yet, much less the racial traits finalized. We don't have the new skill trees decided on, let alone implemented. Source Skills right now are all placeholders, not finalized. Without more of that stuff done, the arena mode isn't going to be great for balance testing.
At this point, with so much incomplete, is there really much useful feedback Larian could get from an Arena Mode test? Larian has to get something out of such a release as well to justify the work it would take to get even a small arena mode public test working.
