Wobbly blades eh? When my blades start the wobble i can expect catastrophic blade breakage in any second. And then BAM, scares the crap out of me every time. In my experience an oscillating blade is caused by either a warped or bent blade, a less than flat tire, or the tracking is off.
WM or at least older WM mills (like mine) use B57 V-Belts as tires. The cheaper belts have a ridge or bump that cause the blade to hop. Higher end belts are usually smoother all around (Pro-tip #1: Buy V-belts at NAPA or Carquest, not TSC) Not sure what brand you're using but a ridge can be found easily by feel. Sounds like the tires isn't the issue anyhow.
Timbeal is right about the tracking but I've found a good 3-4 seconds of full speed spinning is required to see what the blade is doing. (Pro-tip #2: take the guards and covers off for this operation, stand back and away from the dust chute. A broken blade flies outta there like an arrow)
My last suggestion would be to check how round the wheels are, especially if different blades do the same thing.
Let us know how it works out