Necromancer were never supposed to take that high crit damages.
Only bolts had a wrong behavior on necro pets because they used the melee mechanic which allowed for exceeding the crit damage cap.
Here is a patchnote by Mythic clearly stating spells only did 50% crit (phoenix 35%) against necromancers like regular players.
> Bolts will no longer do up to 100% critical damage to necromancer pets; they cap at 50% critical damage like direct damage spells.
https://camelotherald.fandom.com/wiki/Patch_Notes:_Version_1.78
This was even reported on Uthgard, acknowledged and fixed.
https://www2.uthgard.net/tracker/issue/2399/iframe
In short: Spells against the necromancer pets should do only 35% damage on phoenix like against regular players.
Only bolts had a wrong behavior on necro pets because they used the melee mechanic which allowed for exceeding the crit damage cap.
Here is a patchnote by Mythic clearly stating spells only did 50% crit (phoenix 35%) against necromancers like regular players.
> Bolts will no longer do up to 100% critical damage to necromancer pets; they cap at 50% critical damage like direct damage spells.
https://camelotherald.fandom.com/wiki/Patch_Notes:_Version_1.78
This was even reported on Uthgard, acknowledged and fixed.
https://www2.uthgard.net/tracker/issue/2399/iframe
In short: Spells against the necromancer pets should do only 35% damage on phoenix like against regular players.