I don't have the Tokina, but I own the older style Tamron 90mm macro (non VC) and the Canon 85 1.8. They're two completely different animals as far as I'm concerned. The Tamron focuses really slow compared to the blazing fast USM in the Canon, but that's fine since I mainly use manual focus for macro shots anyway. The Canon is awesome for shooting indoor sports and portraits since it's AF is super fast and accurate. The Tamron is probably sharper, but as I said before I wouldn't trust it to keep up with moving subjects. Newer Tamron VC's have updated motors and don't extend when focusing, but the old style micromotor in mine is pretty slow and noisy compared to the silent USM of the Canon. The Tamron also extends a LOT while focusing, while the 85mm doesn't extend at all when focusing. The 85 1.8 has quite a bit of CA, but that's usually fairly easy to correct in software.
Can you shoot portraits with the Tamron? Certainly, and I did before I bought the Canon... but when choosing between the two, I much prefer shooting portraits with the 85 1.8 for it's snappy AF.
I'd suggest the Tamron if you're shooting only macro, and the Canon if you're going to be shooting a variety of subjects. The tubes are a good idea. I've got a set but have never used them with the 85, I'll have to give that a shot one of these days and compare.