Supreme isnt 100-300% better than Trancendent, nor was Trancendent that much over Mythical. Heck, I still find trancendents that are worse than mythicals. Regardless, it shouldn't matter what percent better a new piece of gear is. Better is better.
Well, I actually agree with you here, it is a waste of time to farm. Once you've fully conquered a new piece of content, continuing to do it over and over and over is not a great idea- it doesn't open up any new possibilities, which is part of what a new piece of loot is supposed to achieve.
This is an interesting discussion, but I will set a go