Bah, I should have checked it in game. I forgot about focusing. I remembered 2 out 3 minutes, but misremembered how it applied.
It makes sense to pair Bard and Shaman epics. Same short timer. Helps dps. Gives a platform for everyone to build their burns off of.
Might also be a hold over mentality from when most abilities and discs had longer cooldown timers.
Now, if you care about accuracy, here is what I found.
Bard Epic is a flat increase of 140.
Other ones you may, or may not, care about:
Cry Carnage rk1: flat increase of 20
Quick Time 17+: multiplicative increase of 90%
Thief's Vision rk1 w/ focus is hybrid: 229 * 1.1 flat and +5% multiplicative (doesn't stack with QT)
Now the interesting part. All the flat values are added together before being multiplied.
Ex. Base atk of 1500, using Bard Epic, Quick Time and Thief's Vision.
1500 + 140 + 229*1.1 = 1891.9, but this is EQ and EQ only wants integers, so 1891
1891 * 1.9 = 3592.9, but again this is EQ, so final accuracy is 3592
At the end of the day, these are just numbers. I haven't parsed in game to see how an increased accuracy actually shakes out.