While it would be easy to assume that the open beta test for Diablo IV was primarily to drive game sales, Blizzard has outlined a number of adjustments being made to the launch version of the ARPG as a result of beta feedback. So at the very least it was partially about testing the game for real.
Many of the updates are centered around dungeons, several of which will have new layouts to reduce the need for backtracking. Some of the more general changes to dungeons include an increased chance for dungeon events to tick off and a host of targeted dungeon objective tweaks in order to make them feel less tedious.
Naturally, class balancing is on the docket for launch, with every class getting some targeted refinement as well as more general tweaks to stun and freeze effect duration on elite monsters, a review of all class skills to ensure they can remove CC, and updates to legendary powers.
Other updates coming with the launch version of D4 include a sterner challenge for the Butcher in world tiers III and IV, cellars consistently rewarding a chest on completion, and the removal of the dungeon reset button in order to make way for a new system that will allow for repeat dungeon play. For those who had opinions about the open beta, this set of pre-launch tweaks might be worth the look.