Okay, so you're mixing the two.
As I said, you shouldn't force someone to do something they can't. That's obvious. If a tank/heal isn't geared enough of lack some personal skill, doing big pulls would be stupid and would slow down the run because of unavoidable wipes.
That's a given (hence my "Duh" answer).
However, you are also saying that someone should have the right to do whatever they want in order to enjoy the game. To do what they want "for fun", as you said.
Here's the problem: "fun" is subjective.
If I say to you "I find speedruns to be fun", why shouldn't I have the same right as the person saying "I only find slow runs fun"? How exactly can you tell what kind of fun takes priority over another kind of fun, since it's highly subjective?
Like someone said above, if I find the "normal" strat on T6 to be more "fun" than the LoS strat, should I have the right to tell the 7 other people to go f**k themselves because my fun is more important? Should I have the right to slow other people's progression just because of my own selfishness?
You seem to be saying that yes, I should have that right... but the problem is that, the 7 other people also have that right.
That's why compromises are important in our society and, in that case, a MMORPG.
You can't have everything. Sometimes you'll have to sacrifice your own pleasure in order to keep everything as smooth as possible... because the potential conflict that will ensue will more likely annihilate your "fun" anyway.
That's how human relations work. Compromises.
