Thats sounds like a lot!
I know on the front if I go beyond 7.5° I get a lot of vibration from the drive shaft (JE Reel). I'm waiting for some adjustable upper control arms, but aiming for about 3° or 4° on the front (depending on how bad caster gets), the rear is fine on an Unlimited, so can't comment about the 2 dr rear shaft.
I finally got around to taking some measurements. At the rear, the driveshaft is angled down 14 degrees from horizontal. The pinion shaft seems to be angled up at about 12.5 degrees for an overall "pinion angle" of about 1.5 degrees. To measure the pinion shaft angle, I referenced off of the round machined area on the back of the axle housing.
On the front, the driveshaft is angled down about 6 degrees from horizontal. I had some difficulty measuring the pinion shaft angle at the front but it looks like it's angled up at about 2 degrees for an overall "pinion angle" of about 4 degrees.
The castor looks like about 2 degrees. I measured this using the bottom of the knuckle. I don't know if this is a valid place to measure from but I didn't see any other suitable spots.
I'm going to take the Jeep in to an alignment shop in the next several days and see what they measure for castor and the other parameters (thrust angle, setback, toe, etc.). If there's anything obvious there, I'll have it adjusted. If the vibration persists I'll most likely take it to a local Driveline Service shop and see if they can fix it.
In addition to the vibration, the Jeep handles like a real pig in a crosswind. To be honest, I've never driven any car that blows around anywhere near as much as this thing does. I've had two other Jeeps, both lifted and they weren't even close. Hopefully the alignment measurements will point to something that's wrong and can be corrected.