only problem with fates is that there are people that THINK they are a problem. decreasing spawn would do didly because like DrEvil said, all quests are dried up getting 1-2 classes to 50. as every single class i have never had a problem getting to a fate and doing something usually when i see it spawn or know that its there. I do agree to them lasting longer tho. would feel more immersive as a "fate" right now its just like a popup quest. I have posed this question to many others who want to nerf fates:

what do they hinder in any way shape or form from being the main leveling technique?

the answer is always going to be NOTHING. they do nothing to hinder dungeons, crafting, immersion, fun, or community well-being. If its not fates, its going to be dungeons, then when everyone screams nerf dungeons, fates will once again be the best leveling technique. then what happens? everyone scream nerf fates! the cycle begins anew.