Amiibo cards changed everything. Nobody updates the tier lists anymore.

But there's still a way you can find out where a villager would rank on an updated tier list...just look up their average amiibo card price on somewhere like ebay. It's weird but true. Try it for yourself! Go to ebay, type in 'X amiibo card'(but instead of letter X you put the villager name). Then change it to 'buy it now', and 'sold items' in the options list, so you don't get any auctions. Then look through the list. Generally, you'll find that the more popular a villager is, the higher the average price of their card.
Generally I've found:
$20+: tier S,
$19-$12: tier 1,
$11-$8: tier 2
$7-$5: tier 3
$4-$2: tier 4
<$2: b.o.t.b (bottom of the barrel)
- This only works for series 1-4.
- Sanrio stuff are in a class of their own.
- This doesn't work for WA, because it means that no WA villager can ever reach tier 1 or S class. WA cards need weights, or their own tier list. They're much rarer than 1-4, so they'll always cost more, even the unpopular ones.(Example: WA villager Boyd. Average price for Boyd is about $6. With no weights he'd be considered a tier 3, but considering he's WA, he's a b.o.t.b villager. Compare that to a card like WA villager Stella, who is $25 average. With WA weights she's a tier 2.)
This is just a guideline; it's NOT perfect, so your mileage may vary. Generally speaking though, it works. It's how I've been figuring out how much to trade for villagers since the WA update.