If the data (which was collected by watching video-captures of boss fights for deflects/evades) is right, 10% is pretty much ruled out.
But this sort of visual testing (admittedly, all you can do without a log) seems really error prone to me.
Given that they haven't given us the tools for a reliable in-game determination, it would be really nice if Georg Z or somebody else could just tell us what the melee/ranged avoidance for bosses is.
Accuracy rating causes me to rage when I'm trying to min/max because It's an internal struggle debating what to do with the stat. On one hand I might be losing out on a ton of DPS by keeping accuracy when it's useless. On the other hand I might be losing out on a ton of DPS by not being accuracy capped. Bioware needs to take 10 seconds to post "Yes the accuracy cap is 110% specials" or "No accuracy doesn't really have an effect on your hits".