Wow! Am I the only one who is laughing inside because this same thread existed (a couple dozen versions of it actually) in Beta only replace Dungeon Grind with Open World Grind and replace FATE with dungeons.

Let me see if I can remember the counter-arguments.

1: No-one wants outdated mechanics. Dynamic events (FATEs) are the way forward. If you want dungeons you are an idiot.
2: You say you want dungeons to be competitive, what you actually mean is you want them to be the only way to level.
3: If dungeons are 'fun' as you say, then you would do them with no reward; no exp or drops.
4: If dungeons become competitive exp/hour then no-one will do FATEs which is what the devs put a lot of effort into and what they want people to experience.

Was that more or less the gist of it? It's been a while since someone beat that horse in the forums.