You can also reroll the crystal affix by diamonds but in order to get perfect roll or more satisfying roll try increase the item quality first then reroll it using diamond
After maxing the quality to 25%, I’ve tried using 20/30 diamonds, but the best one I saw was 490. So… how the hell is the eternal one still better after 20 rolls?
for the HP & MP on hit, Crystal only doubles instead of triple, so same value as Epic on Eternal Item. from +250 to +500 instead of +750. I think there is a game balancing reason for this.
Edit: also, Obsidian can be used to improve your Crystal Affix now, not just Diamond. and only a few Crystals can be used on Eternal Items.