I'm currently trying to find a way that I can have a perk which will apply a spell to targets before the player with the perk hits them. I don't think the Entry Point "Apply Combat Hit Spell" will work, since I need the spell effect to be active on the target before damage is calculated--specifically, I want to make various targets weaker to certain kinds of damage when the player has this perk. I haven't tested the Entry Point "Apply Weapon Swing Spell," but I assume it also triggers only on weapon hit the same way as Apply Combat Hit Spell (only in reverse).

Anyone know how this could be achieved?

You can use conditionalized perk entries to increase the damage against specific targets.

This way you wouldn't need to apply a magic effect to the target.

EXAMPLE

The flames spell does 8 damage normally

If your perk made dragons weaker to fire, you could add the following perk entry to increase damage against dragons (by 25%)

Perk Entry

Mod Spell Magnitude Multiply Value 1.25

Then add the following conditions

Spell Tab

S EPMagic_SpellHasKeyword Keyword: MagicDamageFire == 1

Target Tab

S HasKeyword Keyword: ActorTypeDragon == 1

This method doesn't show a damage increase when the flames spell is highlighted in the menu, but when applied to the correct target, the increase in damage is applied.