The rear wheel toe should be around ¼°, not 3°. The camber and caster are given in degrees of angle. The toe in or toe out are given in inches or mm, and also in degrees. These measurements are from the king pin or axle center line for the camber, caster, and toe if done in degrees. If toe is measured in inches, then it is done as the difference from the front of the tire to the back of the tire. As with all tools, an alignment machine is only as good as the person that is using it. If the person does not know how to use the tool, it is worthless. If the person does not understand what the machine is telling them, the information is worthless.
The first thing that needs to be checked is that all components of the suspension are in good shape and that nothing is loose or worn. You need to roll up your sleeves and get dirty to find bad suspension parts. You can not align any suspension that has worn ball joints, tie rods, pivot bushings, etc... as the alignment will not stay true if the suspension is moving. This also brings up something else that is called "bump steer" see: https://duckduckgo.com/html?q=bump%20steer
, or this maybe closer to a Vibe: http://www.motoiq.com/MagazineArticles/ ... Steer.aspx
Old Ford pickups with the twin I beam front ends were horrible at cupping the front tires because of bump steer and bad design.
For rear tire problems the Toyota manual listed "Abnormal tire wear" causes; 1. Tire (Worn or improperly inflated), 2. Wheel alignment (Incorrect), 3. Shock absorber (Worn), 4. Suspension parts (Worn). I would also add from the "Rear wheel shimmy" causes; 2. Wheel (Out of balance) and 5. Hub bearing (Worn). I will also add a bent rim or a bad tire that is out of round. Have you ever seen a tire cutting machine and do you know why they were around? See this for spec's on toe and chamber with drawing for toe: http://madstyle1972.com/Repair/27/200qjl01/i740001.pdf
The rear axle is a one piece unit on the standard Vibe as seen here: http://madstyle1972.com/Repair/27/20ixc/conponen.pdf
If the toe is out of spec and all parts are in good condition, then the rear axle is bent. Either through being hit, damaged, rust through that as weakened the axle metal, metal flexing because of light weight design, etc... can cause the axle to shift and become mis-aligned over time. There are some tapped shim kits that can be used to correct some alignment. The shims go between the axle and the rear wheel bearing hub. The axle can also be bent back into alignment by pulling or welding. There is no easy adjustments that can be done. It requires someone that is knowledgeable about suspensions and is going to cost money to correct. When you see a price for a wheel alignment, think alignment check. It is going to cost a lot more to correct the problem that caused the alignment to be bad.
Alignment shims can be found: http://www.spcalignment.com/component/s ... m&to=USATo
or http://www.moog-suspension-parts.com/ca ... gnment-kit
or others, just Google.