imo a suggested tier fix:
5850 and gtx 470 in their own tier (not with the 280 or 285)
then 1 lower have the: 9800gx2, 285, 280 , (275)*, 460, 465, (4890, 5830)*
then 1 lower have the 260, 5770, 4870
*These ones are faster than the lower tier but slower than the one I put them in.
reasoning, the 470 and 5850 are definitely a tier higher than the rest mentioned above. The 460/465 is also more or less on par with a 280/285 but all four are a tier higher than 260/4870/5770.
The 5830, 275, and 4890 are like a mix.... I would say add another tier in between but that would cause clutter.
Another change imo would be for future articles to remove the tiers that are irrelevant for gaming or at least the tiers with cards that are loooong gone. This would allow you to create more precise tiers with less clutter.
Its all up to you, all in all i always enjoy reading this article plus the CPU one is nice too.