If you can kill the zombies in the cellar and Mira on T6, then you can generally also safely farm Old Tristram road. There's usually a very big group of zombies from the waypoint to Adria's hut. You can farm another unique named Ebeneezer something, and the unique quill fiend in the road leading up to old Trist. Each unique (including Mira) is worth about 4 million XP. Only problem is you sometimes get multiple packs of Es in Old Tristram or the road leading up to it. They seem oddly easy to just avoid, though. Prior to this buff a Mira/Old trist run was yielding in the neigborhood of 40-50 mill XP for 10-15 minutes of work. So, roughly the equivalent of a prepped Crypt run on MP10 pre-patch, which took roughly 30-45 minutes.
If you get bored of Mira/Trist runs, Wizards can do Iskatu T6 runs. Slot back in Archon: Pure Power, slot in Evocation, and melt those shadows. Don't transform right away because Iskatu doesn't show up for about 10 seconds, and when he does the shadows stop coming. When he vanishes, there will be another large wave of shadows and this time they won't stop coming. The god news is, each shadow killed increases your Archon dmg by 6%, so you can easily get up to 1,000,000 DPS in this fight and melt Iskatu. Overall worth about half as much XP, and over twice as time consuming/dangerous as Mira, but not as boring.