Did a little +hit testing last night.
I removed all my gear that had any +hit so that I had absolutely NO +hit from anywhere. No outside buffs either. The only thing I had running was Retribution Aura. I attacked the dummy in Orgrimmar for awhile using most of my skills, then after doing that for awhile I just let my character attack the dummy all night until I got logged out automatically. (I assume it logged me out after the dummy eventually died and I was no longer attacking)
As you can see, out of 5204 melee attacks I missed 249 which ends up 4.8%
This means that there does seem to be an actual ghost hit of ~4% as people have reported experiencing.
My Seal of Blood, Crusader Strike and Divine Storm were also all around 5% miss chance, but there are significantly less attacks from those sources so I decided that they are not good testing platforms. Still interesting information to have to further help prove whats up with +hit.
Currently I'm attacking the dummy again in Orgrimmar without Retribution Aura up for more testing. I'll follow up with that information later.