Prismatic gaze 1 LP over crest of unity 2LP (playing cof and prismatic gaze 2 LP is so annoying to get).
Edict of the scion over elemental affinity fo the last passive points
Would love to hear you opinion on those two matters
No. Crest of Unity provides damage & penetration to Elemental Nova, which we do not care for, since the damage from this build comes from both Frost Claw and Spark Charges 5/5 . This item can be used while still gearing the build, in order to get more points into the skill, but should not be used in place of the other recommended items found in the guide. The only thing about this item that is relevant is the less damage taken, which can be useful but completely unnecessary.
Once you have been able to cap your Elemental Resistances, you can remove the points from Elemental Affinity 6/6 and invest them into other useful nodes, such as Edict of the Scion 6/6.