Why do you need filler quests? What is so important about having some mundane mini-task to collect/kill all the way to max level? Why do you feel you need that?
I don't feel like it's necessary. I would rather have a single large quest that requires me to gear up, get stronger, craft better, group in places and over a span of multiple levels, solve puzzles, discover areas, etc etc. to finally be able to complete that quest. The quest reward would have to be much nicer and MUCH more meaningful than what MMOs are doing today (quest rewards every 5 minutes that add a few more stats). Make the item actually MEAN something to the player as far as value and time spent to achieve it, the places you explored and the people you met while trying to complete the quest over a span of a longer period of time (perhaps a week). Meanwhile you aren't busy collecting bear asses, instead you are preparing your character in various ways to be able to get that ONE quest item. When you get it, it should be very cool, very exciting, last at LEAST 10-15 levels and offer some really cool functionality (not just +main stats).
I don't need kill X mobs and collect Y bear asses every step of the way to max level.
Really you just need multiple long EPIC quests to max level. These quests should take you around the world on a long journey where you meet new people, have chances to veer off and explore other areas and find other meaningful loot and just simply play the game. That's all you need! Not this stupid collect x and kill y shit every step.
When you don't have all these mini-rails to guide you around doing collect X and kill Y quests, the whole world becomes your playground. You make grouping slightly more efficient than soloing and put some emphasis on socializing and multiplayer of ALL aspects MMO - from grouping to crafting to trading to pvping to whatever. You want players to be inclined to interact with each other and get to know each other in good or bad ways, create that community that we all yearn for. This is just BASIC shit that I can't believe developers don't understand, what now, 13 years into the MMORPG genre?
Edit: SORRY FOR THE DOUBLE POST, I thought my first post got deleted.