You are assuming everything is black and white, that is not the real world, it is more like 2 bad apples, 6 people that hover between depending the issues at hand, a lot of people here tend not to speak at all in runs, and 2 good ones.
Some from that middle ground that you do not see is what would be pulled to harass purely based on parsers, while you can have "more harassment" from the 2 in a scope they mouth off worse.
I think you above anyone if you wanna bring your top 20 wow mentality over here would spot that quickly. Tenacity is on gear, if you have something like 780 of it, it is painfully obvious one should make use of 1 meld spot to push it to the next tier. Unless they changed how tenacity works, I wouldn't know, it is SE's fault for not being transparent with their stats to begin with. the 5% comes from assuming if a person can have absolutely ZERO tenacity and that is not going to happen.
The amounts that tend to be argued is 1-3% mitigation DIFFERENCE, not 5%, you can't have zero tenacity.
In a perfect world that would be fine, but the general public does not know how to conduct themselves, thus you have these debates with a producer telling you no. The general player base does not treat things like you do. You are a minority. The problem with "I want people who harass people over their performance to be punished strictly." is not as easy as your making it sound. There are a few things to consider.
1. You cant reimburse time and kick abuse
2. How many threads/posts have you read stating on the lines of "I was about to quit and leave the game over x person acting in y fashion? How many people quit without saying a word? How much would that increase because of parsers?
3. The GM team size is small, it is likely one of the things SE has in the back of their mind, because of the high skill gap, the game's state is unable to handle the volume of calls that will happen with the release of it.
Lastly just because others where able fine tune rotations because of parsers and good for other games, does not mean it is fitting for this one, esp in the current state.
That is why he does not want parsers, you are basically saying people are not good enough to play with, and having to farm that 99 times to begin with is called bad game design on top of things.