It gives some more approximations of base classes not covered by the old tier system, other than that as a mathematical aggregation of a popular vote it is not very useful. It is better to go to the individual thread and read up the justifications of the individual users.
Tier 2 as originally defined by JaronK is neither a weak T1 nor a strong T3. It's a category of its own specifically for Sorcerers and similar spontaneous full casters. Weak T1 slips directly into strong T3, completely passing T2.
