I think this might not be correct. The OP said EK dice are d8’s. If this is true, it is only a drop from 6.5 to 4.5 average damage per dice. It adds additional dice at core 5 and 6, so it comes out pretty close for average damage. It mainly comes down to whether the passive +1 dice at level 20 is still there on top of turning the d12 upgrade into +2 dice. If it is, old was 7*6.5 for 45.5 average damage, and new is 10*4.5 for 45 damage, with the ability to add in elven arcane archer, drow, or other dice without multi-classing.
If the level 20 passive dice is lost, (so only +2 total), it becomes 45.5 vs 40.5 - so an initial loss for pure classed, but still ways to make it up.
The variance will be less with the new system, but especially if that passive level 20 dice is still there, it seems like EK did not get hurt by the change…. And elven EKs can do a lot of extra damage now, if you invest the APs.