Numbers are with max damage. (shadowsun pieces + elite trueshots)
Pre-patch: 218 x 15 = 3,270
Post-patch: 289 x 15 = 4,335
Difference: 1,065 or 32%
Mask phase:
Pre-patch: 149 x 15 = 2,235
Post-patch: 239 x 15 = 3,585
Difference: 1,350 or 60%
Whoaaaa
It's because of how damage calculation works. The resistance reduces by exact number, not by percentage
On mask phase, it has some resistance. Let me give you rough math calculation (I know it's not exactly right)
Let's just say your damage is A = 220, and mask resistance is B = 70
Mask Phase
Before update. A - B = 220 - 70 = 150
After update, A * 1.1 (gun) * 1.2 (charge) - B = 290 - 70 = 220
Normal Phase (no resistance)
Before update, A = 220
After update, A * 1.1 * 1.2 = 290