With the current design it's just pointless. The only way it would work is if the "defense" mod was higher than the offensive mod. Something like let's say offensive magicite is +20 but defensive is +40, then there would be more worth in having it split like 3:2 because the defense would in theory allow you to DPS more efficiently. However since the ratio is 1:1 regardless of where you place it, it's just better to go full offense because in the small scenarios in which the extra defense might allow you to keep your DPS without pulling back, you are losing that overall DPS.

Basically with your example of the 3 pulses that only occurs near the end of the Pazuzu fight, so for the first 5 mins those extra defenses does nothing for you but then in those last 3 mins it does. It it just better to deal 500 dmg the whole time and lose 10 seconds from the pulses than to deal 300 and ignore the pulses.