Quote Originally Posted by ohjel View Post
At least according to the edit screen, even the raw stats of an acc are also only for the character equipping it. So 500 att will be better, but not massively better. A more interesting question would be how 4% double att chance compares to 500 att.

Realistically though, you shouldn't be spending any effort on leveling your accs until you get good ones.
Normal attack damage is about 50% of damage output. I expect a 4% double attack rate increase to increase the average attack rate by a little less than 4%. So damage would increase by a little less than 2%. The effect on Burst damage depends on what your bottleneck for Full Bursts is and whether you're addressing it. 4% double attack on all characters would increase Burst accrual rate by a little less than 4%, buffing Burst damage proportionately.

Meanwhile, I reconsidered the effect of additional character attack, and additional character attack should increase damage by about 46% of the character attack value (2.6% for 6%) in a maxed team using 2x +45% elemental attack eidolons. Meanwhile, +500 attack will increase damage by about 1.3%.