The foundations of your reasoning are partly laid on false assumptions and misunderstandings.
Steve wrote:All characters are fully playable. This says nothing about mechanics, nor Tier 1, Tier 2, etc.
I obviously meant mechanically playable in a Tier context. Everything you can log in with is "playable", but that was clearly not the point. The problem is, knowledgeable players know almost everything has Tier 1 and Tier 2 build options at the very least, and Tier 2 means strong. Notable exceptions were classes like Barbarian and Swashbuckler, which had particular issues in a percentage of the server areas that was deemed too vast, and thus they have been revamped to solve the problem.
I'm not arguing that Players are right. I pointing out what players often request...and they get it denied plenty because yes, BGTSCC is not a vacuum and the issue of power creep is taken into account...except when it isn't.
Developers make mistakes too. It's easy to underestimate a coefficient or a particular ability, when you have a lot to code. For free. When "it isn't", it's not intentional.
This might not be a competitive game, but plenty are playing it that way. PvP for the sake of "braggers' rights" has always been evident on BGTSCC.
That's a player problem. Devs can't redesign people's heads. Not to mention, crying on the forums for buffs or nerfs is the real shame. Certainly not losing PvPs in a cooperative game.
I'm not dogging QC here, but it is correct to see how supposed Top Tier classes/builds have benefited from recent custom changes...but even then, I'm not complaining about the result because I enjoy the result! But let's face facts: those changes came about because a Dev got the mind and had the energy to do the work, and otherwise, that Content would never have arrived. Which is important to say because this thread actually hit a good note in reaching a supported conclusion that if a Dev wanted to make new (balanced) forms for Word of Changing, that change could find legs.
So, Devs don't always consult QC before introducing changes, and are generally not as experienced players as QCers are. QC gives feedback on what's problematic, numbers get tweaked when someone has time to do it.
This isn't a company. The process doesn't need to be perfect. It's already a miracle it even exists, since there isn't a dollar in it for anybody, and the game's too old, and bugged.
Leveling the playing field HAS been a concern in the past multiple times on BGTSSC. Maybe it is not a general concern, but often enough a Class, PrC or custom content gets a nerf. Balancing = leveling the playing field.
There you go. NOPE!
The reason the content gets nerfed is to keep it in line with the playing environment and, reflexively, DM events. You can't level the playing field the way you describe, because in D&D, the playing field is NOT level. The point is for every character to bring something UNIQUE to the table. NOT equal. Actually, the OPPOSITE of "equal"

.
Example: Hierophant vs Warpriest vs Thaumaturge. Are they all balanced with respect to each other, power-wise? NO. Do they all bring something different to the table, mechanically speaking as well as RP-wise? YES. Are they all worth taking? YES. Is any of them a balance concern? NO. You can tweak them IF A DEV HAS THE TIME, but it's not considered worth of a dev's time.
That needs to be clear, otherwise everything you say is based on different criteria with respect to QC. No wonder your expectations aren't matched.
It is stating the obvious that nerfing Tier 1 requires knowing what to nerf.
It's not obvious. Even a knowledgeable player like Nemni, with a 2009 account and a place in QC might not know Warlocks are Tier 1.
This game is very strange. Documentation is far from exhaustive, and even when present, often contradictory. The playerbase isn't (and has never been) big enough to have explored everything the active development of BGTSCC has to offer, mechanically speaking.
I made a MaA in February, and it quickly demonstrated you don't need a Dwarven Defender to be a Tier 1 non-caster. Because that was the stance, back then. Now, it's suddenly clear to most MaA is immensely powerful.
Spirit Shaman has been considered "bad" for ages. Some say Sorcerer is "weak". Fighter "underpowered". We had arguments on Bard needing "a buff".
I mean...I could go on. But by now, I think you see my point.