That is the gigantic problem right there which skewers your perspective of things. A team of 6 Pokemon; especially excluding Exp Share / Lucky Egg, will significantly lower your level output. With 4 you likely wouldn't even be 5 levels behind your opponents if ever. I mean I get the call out on researching against me (but ffs I seriously cannot remember everything every Pokemon learns and I don't have access to a database that has it... unless others do), but come on if we're playing the tier list game let's at least be consistent with the tier list goals (like using a reasonable amount of Pokemon in a team).
When Mekkah was in charge of the RBY tier list, people piloted theories arising out of discussions by playing through the game with 6 Pokemon, so I'm not making up anything new here. That was a much easier gen however.
Team size is just one of the many things affecting tiering. Exp Share makes your level advantage huge no matter the team size - we agree to discard it. Lucky Egg can be meticulously used on your lead every time and give you 1,5x experience after a certain point of the game.
There's another thing you could do to maximise exp gain which is to switch all of your 4-6 Pokemon in against every single enemy you encounter - they will all get the same sum of experience and the effect will be even bigger than from using Exp Share (the switching will take time though).
I think the tier list should account for a multitude of situations, including different team sizes (6 and not just 4 for example), exp groups (a full team of slow/erratic will be underlevelled no matter the team size) and peculiarities of capture (the hoard-only exclusives are terribly underlevelled sometimes and pull the rest of the team down in levels).
Should you have a worse nature / poorer IVs, a Pokemon that is expected to outspeed may fail to do so and get OHKO'd before managing to achieve the same, or one that's expected to OHKO may miss the KO and receive heavy damage back. As a rule, everything that's good at a higher level is also good at a lower level in relation to the same Pokemon, but if we were to include Exp Share into this (or had all the time in the world for full-team switch-in parties) something like Furfrou would be functionally equal to Roserade, or even better due to having more diverse coverage.
We simply need to account these instances.
Also conceding Gyarados to A. After thinking about Aqua Tail in Gym 6 and 7, the only issue is bypassing Slowking (unless Meowstic / Sigilyph have something like Charge Beam / Thunderbolt). It OHKOing / 2HKOing everything is doubtful to my knowledge once it is a Gyarados (well okay, 2HKOes definitely with Dragon Rage and OHKOes on squishymons). But at least past Clemont Gyarados should be doing alright. For what it's worth, Gyarados makes a decent HM Slave too with access to Waterfall / Surf / Strength / Rock Smash. This is pertaining to Gyarados caught via Super Rod, by the way, and not trained ones.
Trained Gyarados has more time to contribute and, as a result, gain EVs and perform better than a Gyarados caught late pre-evolved.
I really think we should tone down the focus on HM slaving, though. How about we only credit to Surf/Fly/Waterfall on phys-oriented water mons? Bend it to emphasise what these moves do in-battle.
Though I want to point out comparing Magikarp to Raven is an insult to Raven since Raven actually does, well you know, damage around that part of the game. The best comparison I can think of is if somehow FE7 was stretched a hell of a lot further and Nino only had access to Fire.
Nino would be great if she were "stretched out" with Fire, but who cares about E staved on promo anyway. Regardless, when I brought up old FE tiering I implied that XY tiering is completely different (so I'm intentionally not comparing anything or trying to find serious equivalents between this and say FE7).
There is also nothing wrong about being delegated as an HM slave. Again, it's why I actually could go with high C / low B Hawlucha. Hawlucha actually does decent up until the 6th gym and can be useful outside of battle after that point.
Hawlucha sounds worthy of B even if we forget it's a viable HM slave IMO.
Raising 4 mons is a lot better than lol6 anyway.
Raising just one Lucario is also a lot better than a team of 4; what's your point?
You keep picking on this point after I mentioned raising a team of 6 slow exp mons, but you haven't yet justified why you encourage to dump exp into an HM slave and drop them later on - how is this consistent with you motivating us to keep the teams small? Still waiting for that justification, even moreso after your recent post.
Sorry, lack of strong rock stab. Stone edge is both inaccurate and late, not to mention it has 5 pp. Rock slide's tm is postgame, while aero doesn't get it by level up until level 73 which is not a level you're likely to reach even WITH exp share.
Pretty sure you get Rock Slide as soon as you get access to Waterfall.
Still, I could perhaps make the argument that having to do research into what Shedinja can/can't survive against is a pretty heavy opportunity cost, though. The issue of grinding levels with Sheddy is still a huge issue (you pretty much have to check level moves for every Pokemon you run across, unless you're grinding on the same wild Pokemon for a long time), and having to check whether or not Shedinja is going to die instantly can be time-consuming IRL. (And that's even ignoring the fact that Shedinja is slow and has shit-all coverage when you get it.) So that said, I stand by my previous claim for F-tier on the basis that it's too much of a hassle just to raise Shedinja for long enough to fight Korrina even. (Nincada comes about the same time as Honedge, so there's a lot of grinding it has to do just as weak-as-shit Nincada before it evolves, and THEN all the careful grinding in the towns leading up to Shalour).
I think a good start would be playing through the game with Shedinja while checking/studying all the learnpools available (you have
just 5 weaknesses to be concerned with). Maybe my belief in generic mons' movesets being set in stone to their level is one that doesn't match reality. Still, being limited in what he can switch into should limit him to D tier, I would suspect.