[1.0.3.1] Wrath of Callidor: Return of the Glorious Melee Sorcerer (u)(c+)(g3)(vid)

I read that flat DA/OA reduction don’t stack, if more than one source is applied at the same time - only the highest proc counts.

It follows the same rules as RR.

2 or more sources of flat OA reduction do not stack, same goes for flat DA reduction. OA and DA debuffs are independent of each other and follow normal stacking rules as RR so flat OA and flat DA can stack together.

See this chart to see that OA reduction and DA reduction are in their own spreadsheets, hence do not interfere with one another.