I see what you are saying, but I think you have misjudged full-blooded Vulcans. They quite often fall into the stereotypes of Straw Vulcans, though they may do it less than Spock.

To be fair on both Spock and the Vulcans the difference seems to be how much screen time they have in which they happen to be the most suitable target for one of the more preachy writers. For example a Vulcan fortunate enough to be in an episode with Data is mostly protected by the even more convenient android target.

Given that T'Pol is from the Enterprise series, I'd discount her as a source of evidence about the Vulcans as depicted in the original series: Enterprise is too far removed from TOS, and everything we see in it might be brain bugs.

Do you remember the telephone game from grade-school? All of the kids would sit in a circle. The first kid would whisper something in the second kid's ear, who would turn around and whisper it to the third kid, and so on. By the time it came back to the first kid, the message had completely changed. Similarly, when you have many writers working on one show, each new writer tries to interpret the work of the writers that came before, and then extrapolate from it.

It's easy to see how this works like that old grade-school telephone game. Writer #1 creates a fictional universe. Writer #2 creates a story set in his interpretation of Writer #1's fictional universe. Writer #3 creates a story which is set in his interpretation of Writer #1's fictional universe, and which attempts to continue his interpretation of the story written by Writer #2. Writer #4 tries to write a story which is consistent with the story written by Writer #3, and which is set in his interpretation of Writer #1's fictional universe, but he's not too familiar with the story made by Writer #2 because he never saw it. It's pretty obvious that by the time you get to writer #50, you've got a real mess on your hands.

But this mess is not entirely random, unlike the telephone game. People have a tendency to simplify concepts in their minds because, well, it's easier that way. We see this most prominently in the case of racial stereotyping, where racists simplify an entire human race into one or two key characteristics. It seems to be an innate tendency that can only be solved through education, which may help explain why racism tends to be inversely correlated to education level. The same mentality which drives racism seems to drive many of these brain bugs. Rather than think critically or thoroughly, it's easier to seize upon the most visible or interesting characteristic and then simplify the situation so that nothing remains but that lone characteristic. And in the Berman-Braga age, simple-minded thinking is the order of the day.

It's important to remember that this is cultural. Remember that Vulcans are the same subspecies as the highly emotional Romulans, only separating a couple of thousand years before the setting. There are real-life humans who are worse than T'Pol for that sort of thing.

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Indeed, there are many full-blooded Vulcans that are also written as huge jerks. According to the Star Trek writers, Vulcan logic and mental discipline don't seem to have much to do with whether one is an asshole or not.

You're definitely right about Sarek, but I've not seen Enterprise, so I'm not familiar with T'Pol.