Why aren't you all using Overpower?!?!

Its this way because it is the strongest stat, for all classes, for all builds with the sole exception being those who rely on overpower.
Every class can go from +20% vulnerable to +100% vulnerable, by using the glyph and priorizing it on your equipment.
This also makes the largest difference, because it is a 3rd multiplier.
This means you are using your previous damage more efficiently instead of diminishing your own values by sheer size.
Assuming you would be at 100% critical strike change, your base damage would be
100 (total sum of your damage modifications)
+50% (critical strike damage base) +20% (vulnerable) = 180
Now looking at the strongest roll of critical damage vs vulnerable you would change to
+67.5% +20% = 201 or
+50% +34% = 201
But hey, you arent going to have 100% critical strike chance, so vulnerable wins at this point :wink:

You were seeing a 3% chance happening.
Should be happening much more often than finding a good item.