First I agree Vaporeon is better than gyarados. i think we all can agree on that, don't even need to point anything here.
On your first Gyarados points, you focused on explaining why he isn't good for any specific matchup. I agree he is not. But as a genralist:
You say Dragonite or Tyra are better. Of course they are but see their rank on your list Dragonite is tier 1 and Tyra 1.5. Gyara is placed rank 3. The distance between them is not that high. As a generalist Gyara is preety good snce he is only weak to electric (very) and rock (little). Did you see any electric guy defending at any time or even rock (a bit more cummon but not cummon at all) around?. If you focus on gyara weakness and strongnest you can see he is perfect for attacking anything. With decent HP, high attack, nice move set and no vulnaribilities, it deserve rank 2 or at least 2.5 in my opinion. Why?
All on rank 2.5 have low hp and good attack. They are good with dodging. But isn't Gyara better in any case? Any of those would perform worst than Gyara while attacking a gym with dodging, dying faster. And I don't see any matchup on them except grass on flareon/Charizard that isn't cummon at all except exeguttor. Not to mention the psiquics or Gengar. Also depending on the Gyara move set he could be good for Dragonite (dragon moves) or Rhydon (Hydro pump) or even with crucnh (psiquics and exegutor). SO maybe he is not an specialist but performs good too against most cummon defenders. Not to mention how resitent he is to Vaporeons.
Don't know you but myself can't think charizard or flareon are better than gyarados for anything except fighting grass types and even there maybe gyarados would finish faster. Same goes for the others on tier 2.5. It's like a joke they are better and i was never a Gyarados fan just saying my toughts.
I think you focused this list too much on the machups, placing them high (as you admited with Lapras), leaving the others on the very buttom of the list.
But the reality is that nowdays with the gyms crowded with dragonites, vaporeons, rhydons, Tyranytars and gyarados this list doesn't reflect that good what are the best choices for everything Maybe I could agree on tier 1-2 but the rest... doesn't suit the reality in my opinion, with all respect for you and your list.
Regards,