With the patch now out just a suggestion for future betas regarding the below line:
Beta characters have access to a copy of your account's Legendary Armory. Legendary items newly added to your Legendary Armory while a beta event is in progress will not be usable by beta characters during that beta event.
Maybe give the beta characters access to the full armoury (all armours, weapons, trinket, runes, sigils, etc) instead, then every player is able to test out any build, stat, weapon they want during the beta period