By my estimation, there’s about 30 very active, participating trainers in the amiibo tournaments scene. A few come and go and are replaced by new ones, but for the most part we’ve stayed at about 30 for a while now, even before the 3.1.0 update. It’s a cozy little community, and still much larger than the Smash 4 one was at the end of its life as far as I can tell. We’ve got our quirks, like the unofficial Gentlemen’s Rule that we don’t submit Bowser to tournaments (although occasionally sending him is fine), and the odd habit of repeating “Joe” whenever someone says the name in chat. With few exceptions, though, the amiibo scene is a quaint little place.
However, Ultimate is a much larger game than we can handle. As of this writing Ultimate has about 68 characters representable through amiibo in some form (unless you count Squirtle, Ivysaur and Pokemon Trainer as their own versions, and it seems likely they will each have slight variations on the Pokemon Trainer character when they release). 68 amiibo to manage information on, and 30 trainers to train them. That’s a lot of plain ol’ stuff to train and maintain. That means each trainer has to train a little over 2 amiibo per person, with no repeats, and regularly submit them to tournaments in order to have accurate information on them, which also requires that we have enough tournaments regularly to be submitted to.

Obviously that won’t happen, and hasn’t happened: it’s far easier to get your hands on a Link amiibo than it is a Mii Brawler amiibo (partially due to recently released alternatives like the Legend of Zelda series), so those characters are entered more often. Also, everybody has their favorite amiibo and they’ll keep entering them no matter what, such as my Mii Swordfighter, Corey. There are many, many reasons why people send in some amiibo more often than others.
Ultimately, we see this impacting the metagame. Characters with much more representation tend to perform better simply by the law of averages – the more often you try, the more often you win. This is even evidenced in the June 25th update of the amiibo tier list: note that in the bulleted section at the bottom, the word ‘represent’ in some form makes an appearance four times. Nine characters were moved, and representation or lack thereof was cited as being a factor in their new placement on the tier list. It’s nobody’s fault, but it is apparent that characters that are entered more often win more often, to a degree.
There are limits to the above statement. Bowser, for example, doesn’t get entered very much thanks to the unofficial Gentlemen’s Rule. When Bowser does get entered, more often than not he sweeps up quite a few matches, even if the Bowser is poorly trained. (One of these days, remind me to write up a post on the Bowser that I trained exclusively with Journies.) Many trainers have recently entered the Ice Climbers and have had no success with raising their place on the tier list, either.
It seems moreso that representation allows amiibo with potential the chance to shine, while the unrepresented amiibo with potential don’t. My Rosalina’s recent victory at Not Amiibrawl 5 is a good indicator of this. Rosalina is a character that isn’t often submitted to tournaments, which resulted in her placement in D Tier. I trained my Rosalina out of sheer boredom and sent her in to a few tournaments, and of the four I sent her to she placed well in one and won another, then flopped in the last two. Giving Rosalina some representation resulted in her showing off some potential.
There’s really no way to solve this problem, aside from bringing in lots more people and many more tournaments. If you’ll recall my post Making a Meta, I said that the more time and people a metagame had, the more it would discover (which I referred to as ‘Labor’, but that was a clumsy word choice). In this case, we haven’t been around for a long time and don’t have that many people, so we can’t yet adjust for the limited representation that some assumed bottom tiers have.
I guess in the short run, we’ve just got to enter amiibo we haven’t seen in a while, right?