Two questions about class/tier comparisons [a bit of a rant]

[TuggyNE]

The point that the OP is making is that, when talking about the utility of a druid, it shouldn't matter (much) whether a wizard can counter them.

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The Arena Fallacy is a fallacy because most (or at least a lot of) D&D combat is a group of players against enemies which may or may not even have class levels.

Yes, exactly.

Edit: As for *why* that trend exists, I think it's there for a few reasons. First and foremost, it's simply easier to think about than this nebulous idea of "the average of all encounters", or whatever other alternative is there. Second, there's a fair bit of human nature and societal norms built around direct confrontation. It's the same thing that leads to a fist fight over who's better at a sport.

These are both fair points. I don't suppose there's much that can be done about the second one, except to try to discourage it where possible; the first, though, can perhaps be reduced by formalizing condensed "standard" encounter sets. E.g., a set of four-five widely differentiated encounters with which to compare the classes, either by running them through, or simply theorycrafting. (Essentially, the encounter series Psyren mentioned, standardized.)

I do not think is a fallacy at all: the simple fact that in a campaign you could face enemies with class levels means that you should be aware that a Wizard has many options against a Fighter, while the Fighter has few option against a Wizard. Of course this is just an example, no intention to start a debate Fighter vs. Wizard. I just want to point out that an arena fight could be a good way to see if a class could be a reasonable challenge to the party and if not, what kind of tweaks it requires to not utterly destroy it, or give it a good fight.

This is true, as far as it goes, but the fallacy lies in trying to use the comparison for more than it actually works for. Fighters are a fairly good stand-in for all kinds of mundane classes and monsters, but what about a comparison of Shadowcaster vs. Truenamer? There are very very few monsters that use either of those subsystems, and not too many NPCs for that matter, and a direct arena comparison is therefore next to useless for determining their respective value in a party.