Glass Cannons cancel Great Magic Barrier?

So I went into a gank and this guy casted GMB as I was dealing with his phantom. At the time, I had Pursuers and was buffed with:

1) Tin Crystallization catalyst
2) Crown of Dusk (30%)
3) Bellowing Dragon Crest Ring (25%)
4) Power Within (40%)
5) Red Tearstone Ring (50% to raw damage)

So the host comes in with that 90% damage negation and triggers all 5 pursuers by accident (Real accident because I was locked to his phantom). So I roll out of the way as he and his phantom synchronize attacks and...

All 5 pursuers hit, hitting him for 700+ damage through his magic barrier, instantly killing him. This actually picks at my interest as I had tested that Pursuers have 800 AR each at this point, maybe even 1000 if I remember wrong. Since there are 5 of them, the AR could not be higher than 5000, which would mean he would only take 500 damage at most.

So this leads me to believe that percents are cancelling each other. The combine damage bonus from all my items (minus the RTSR's raw add) is 95%; 5% higher than GMB. So, all the percents cancelled each other and that left me with 5% damage bonus on top of RTSR, rendering GMB ineffective.

What do you think?

I believe someone proved that Dark Magic was magic damage plus physicall wich means It didnt cancel anything. The extra damage was probably for the physical AR of the spell.

Crazy

I tested Gmb against dark magic with high int and Gmb works well( took like 300 damge I believe.) However that was not with power within/rtsr. Im sure with enough boosts and low hp target. Gmb wont make a difference.


EDIT: What is your stat layout?

23 ATT
50 INT
Everything else base Sorcerer
Sl 47

Pretty basic Glass Cannon for the forest.

I had tested my damage outputs on Dreglings and I can say that Pursuers can have an AR of 5000 when fully maxed.

What could have happened. Since pursuers always have some sort of physical damage(If I am right). The Power Within could've amplified that by the 40% and the rtsr by the 50%. So pretty much just destroying the guy with physical damage... However I would have to do some test just to be sure....

That is my 2 cents to what could have happened.