It wasn't meant to be endless as evidenced by damage/health increasing per level. Data showed that players were spending 2+ hours getting to wave 600+ in a single session -- that's nuts. Although that's how it has been, that's not how it was meant to be and it wouldn't have been endless to begin with if the bug hadn't existed in the first place. We found this issue a while ago, but waited until a new season to introduce the fix.

We may choose to adjust difficulty in the future, but that will be after we've had a chance to look at the data after it has been stable for a while.

-ALS