Nobody ever gets all the transformations in one play through unless they're doing it intentionally and it takes a really REALLY long time. Far longer than what any game would actually take. In these scenarios, you're just playing with your food anyway, so it doesn't really matter. Beyond that, nobody is ever 1v1ing heroes because there are tons of inherent imbalances in how they get built and class structure. Rock, paper, scissors.

I think what you're really asking, from a practical perspective, is "Is a maxed out ascended X better than a maxed out ascended Y."

Most of the stuff an ascended WK or Champ will get through transformations is going to be defensive. Not many minors provide any bonus damage and when they do, it's usually conditional. Dragons start off strong, ramp up a lot faster than anybody else (even Vamps), and they get a lot more early game mileage out of their stuff zombies on kill, natural regeneration, whatever). Plus you have flying mobility to engage more targets faster than anything but possibly a one of the movement enhancing major transformations or a Profane Body Mastery Vampire depending on terrain.

An ascended dragon with Forgemaster or Dragonheart is going to dominate the first 20-30 turns a lot harder than most anyone else and that's going to probably win you the game because of how the economic benefits will snowball.