Strands of Astral Power. Worth it?

[Jazzepi]

Tuidjy said:
Jazzepi, the enemy mages in my dominion range from MR 18 to 26, with the majority
at MR 20. The difference between Drain 2 and Magic 3 is 3MR. That would give
a bonus of chance of 8% (Wowsers!) for the wimpiest targets, and no appreciable
bonus for the tough ones.

Mine is a simple argument. If the spell depends on the modified magic resistance
of the target, it should depend on the modified penetration of the caster.

Oh, I agree! I still think the spell is fine as is. shouldn't it just demolish armies that have non-astral, and thus lower MR, mages?

Jazzepi