Classes with a large amount of utility and buffs such as Thaumaturge or Priest will always scale decently if you put them into a build.
Classes such as Pyromancer will inevitably become nothing more than filler damage in between your actual damage combos in the late game.
The reason for this is that the power of buffs seems to stay consistent throughout all tiers. Additionally, many utility classes provide unique buffs, meaning that there’s no competition. Meanwhile, damage is mostly numbers. There’s classes like Cryomancer who can present helpful CC when their damage stops being effective, but that’s a unique case.
This complaint is coming out of my attempts to make a build where Pyromancer could shine. In almost every case, Psychokino or Warlock were simply better options than investing into Pyromancer at all. I don’t think it’s right that early classes don’t scale as well into late game. If you go to Pyromancer’s 3rd circle, your damage shouldn’t suddenly become nigh-useless once you have a T6 or T7 damage class.
A later tier of classes should give you new options to include in your damage cycle or ways to cover your offensive weaknesses, such as not having enough AoEs, but they shouldn’t obsolete your existing skills.
EDIT: I’d like to add that I don’t think there should be no “wrong way” to make a build. I’m just saying that a DPS class brought to C3 shouldn’t be obsoleted by a later DPS class at C1.