Resurgence introduces a revamped Crafting System that utilizes new crafting items. There are two tiers of crafting: basic crafting similar to crafting in Diablo 2 and divine crafting, a more end-game crafting using Divine Crystals and new crafting items.
Diablo 2 LOD crafting created an item based on several numbers, Your level, the items level, the monster's level that dropped it. These numbers determined the bonuses an item could recieve. Resurgence works in a similar way where the different crystals will determine the items affix level(alvl).
Blessed Crystals will produce an item with Item Level * 0.9 Affix level
Regal Crystals will always produce an item with an Affix level of 94.
Divine Crystals will always produce an item with an Affix level of 99 and double the inherent gem bonuses.
Worldstone Crystals will always produce an item with an Affix level of 99 and triple the inherent gem bonuses.
Rare and Crafted items also have an expanded bonus pool. Any affix that could roll on a Magical Item can now also roll on a rare or crafted item. As well many bonuses will no longer spawn the lower end rolls if the Affix Level is high enough.
For example alvl84 Amulets will no longer spawn with the low end STR bonuses such as of Strength(1-2), of Might(3-5), or of the OX(6-9).
This change means higher level rares are more commonly useful. For more information on Affix levels and available bonuses check out The Arreat Summit. Resurgence has not increased any required Affix levels.