I've noticed that Blitzstrahl seems to have more difficulty than other spells to process magic weakness!
I assume this is because the spell has additional effect: Stun and proc'ing while stunned doesn't seem to work..
Removing the stun =/= proc would fix this and save a lot of headache.
And it's not the correct forum, but can we change all magic proc'ing so that casting the correct spell under the correct conditions (when monster is not casting/tping etc) will cause proc, whether or not the spell lands?
There are many situations where the correct spell to proc a mob turns out to be a status ailment or element it is immune to.. removing the condition that the spell must land will fix this.