When I tank, I look at party make up and ask how they would like it to be handled.
When I dps, I listen and go with the flow.
When I heal, if I feel like I may not be able to pull off healing a huge mob I'll ask for smaller group pulls.

Common sense, being courteous, and doing your best to get along with others and work together to achieve your goals. Really not that hard unless you just enjoy the drama. Don't feel like speed running today? Maybe avoid the popular speed running spots if possible, do things with friends if you want to take it nice and easy, there are a variety of ways to approach the situation. Also it isn't actually a "mechanic" of the game for people to speed run, it's a player choice, and we live in the I want it now times. SE does try to find ways to cut off speed running, but there will always be a way around whatever method they come up with unless they build each room in a dungeon like Halatali Hard mode's humanoid party mobs section.