I thought Grenoldt used the damaged crystals from Ardbert's friends to craft your AF5 sets? Or at least used them for the 'inspiration' he was previously lacking.

As for our Crystals, they still play an important role past HW - they're how you manage to store the corrupted Light aether you absorb by killing each Lightwarden during ShB (or at least, the Blessing does, which is powered and sustained by the Crystals). However, not even the full eight Crystals can hold the combined corrupted Light essences of all six Lightwardens, at least until Ardbert rejoins his soul to yours, and then helps you expel it by using the corrupted Light to form an Axe of Light to punch a big hole through our Ascian bff.

The Crystals definetely are still an important part of the story, they power the Blessing of Light which is a very important part of the WoL's powers.