I just had a rather odd battle involving vampires, Thalmor, Vigilants, wolves, guards and a Legate. And me, of course.
It was at the crossroads near Falkreath Watchtower, where there is a random encounter area.
Three Falkreath guards and the local Legate were heading in the same direction as I, and thus got involved in the battle.
First I saw what could only be vampires (the red drain spell thing is unmistakable) fighting something. At this point the guards drew their weapons, however I couldn't make out whether everything ahead was hostile.
It soon became clear that there were no friendlies there, so I started shooting at the nearest vampire. Only to get attacked by wolves, and then by the vampires.
Arrows and bolts were flying, and I was constantly being drained (the vamps were weak, and the spell did next to no damage). All of the vampires targeted me, and thanks to SkyRe's improved enemy AI surrounded me. I struck them down one by one, while the guards + Legate were fighting something else.
After it was all over, I discovered two Thalmor corpses (took their armor to smelt it down), two Vigilant of Stendarr ash piles (hah) and a bunch of wolf corpses. Plus the three vampires, obviously.
It was quite an intense battle.