Thanks for taking the time to respond.
Basically what I am seeing is a decrease to my dps of ~5% when the attack speed buff from ASE is running.
In the screenshot below the first 4 Power of the Woods Spirits are with the attack speed buff active and the last 3 are after the buff has run out. I had no other buffs/debuffs and the mob had no buffs/debuffs.
http://img339.imageshack.us/img339/9964/66624704.png
If I perform a similar test with Joint Blow(which is not affected by attack speed) the the damage is unchanged by the ASE buff. The only explanation that I can come up with is that the buff from ASE is decreasing attack speed, but I don't know of a way to check attack speed directly.