Exponential inflation is bad, okay?

Q u o t e:
It's bad game design, it just is. In vanilla, character and gear growth followed a linear formula, and someone in blues at level 60 could hold their own against someone in purps because the difference was only moderate due to the linear progression of gear, item levels roughly followed character levels and PvP, while still heavily gear dependent, was at least in some way dependent on player skill.

For whatever asinine reason, they decided that exponential growth was a good idea when BC was being developed. Why? Now, gear makes way too much of a difference with regard to both PvE and PvP, which has bad gameplay repercussions:
a. it stretches disbelief to go from 4k health at level 60 to 40k health at level 80.
b. it's harder to balance bigger numbers
c. content is trivialized way too quickly and easily
d. PvP is bonked and imbalanced. A level 75 should be able to hold their own against a level 80, but because of the ridiculous exponential growth of stats and gear as you level in the latter levels they can't. Nor can a level 80 in blues hold their own against a level 80 in purps. Why does no one realize how horrible that is?

Player skill should be more important than gear when you're talking about toons that are near the same level. Even though it still made a difference, it was much better in vanilla when gear and player skill were nearer to equal importance.

Your'e confusing relative to absolute effects in a couple of cases here. It is not harder to balance big numbers. Math works the same way on big numbers as it does on small numbers. It's harder to balance big numbers to small numbers, which might be a problem if we expected say level 85 characters to PvP against level 35 characters, but that's not how we design the game. It isn't important to us at all that level 75 characters can hold their own vs. level 80 characters. It's more fun to become more powerful as you level rather than see only slight improvements in your stats.

Fresh level 85 content won't be trivialized by level 85 characters until a new patch comes out, at which point it's not fresh content any longer.

The point I think has the most merit is your point A, but I think that one is a worthy sacrifice in order to be able to provide more content and a sense of progression to existing characters.

There's a magic number that we've found over time to feel satisfying to players, and that's about the 13 item level jump between tiers of content. When the numbers are less than that, players see for example their health only go up by 10 or 100 points, which doesn't feel meaningful. They don't feel rewarded for their efforts and have less interest in doing the quests or dungeons or the new PvP season. If players gain a level or two and still have trouble with that raptor that gave them a hard time before, then they don't feel like the process of improving their character is worth it. Everything else is derived for the need to have that meaningful jump.