So this IS your first MMO, then? Here is how it works: Player gets to level cap, further expansion of character is then decided by gear upgrades. Getting better gear often means running large dungeons or raids but key enemies (bosses) will only drop a few pieces of gear to be divvied up amongst the party. Sometimes you get lucky, sometimes you dont. But why shouldn't a boss just drop gear for everyone all the time? Why isn't there a simple algorithm to determine what the boss could drop that is an upgrade to you? Why should you ever have to beat this dungeon more than once?
It's simple, the developers want you to keep playing the game so you keep paying them to play, obviously. To do this, they want to balance the time it takes to achieve the upper limits of your character against the time it takes to churn out the next content patch. Ideally, hardcore players (the minority) will be 'done' halfway(-ish) through the lifespan of a current content patch for which they were 'maxed' out in the patch prior to this one. Ultimately though, players with such devotion will likely play the game anyway whether or not they have done everything. Casual players (the majority) will be reaching their limits JUST before the next content patch so they will always have something to strive for and will continue playing (and paying) because of it.
So how do you fill in that gap? Having no guarantee on gear due to random drops and/or rolling against other players for gear is one way. Naturally, dungeons are designed to impede you... otherwise there would be no bosses, just a room with a treasure chest, go get your loot! Bosses and trash mobs are supposed to block your path and make you work for your gear and you are supposed to fight them ad infinitum until the next content patch arrives.
If it sucks for you, do something else. A good MMO will have plenty of distractions from the 'main' goal of gearing up and gaining power. Obviously it will all become boring if you repeat the same things over and over again but it is supposed to be an investment of your time to keep you paying to play.
And 7 hours to cap for the week? Thats cute. And people say WoW went too casual.
Edit: It's an exploit, but I encourage it. Players will inevitably always find the shortest path to power by ANY means available to them in-game. Someone at SQEX is going to see this in action, say 'thats not good game design' and it'll be changed accordingly. The game only gets better because of complaints and concerns made vocal. It's not as simple as having the mobs aggro onto the entire party in a dungeon... there's a clear reason why players are avoiding the trash. I would like to think that the devs would re-examine how long it takes to clear the trash, adjust their power accordingly if necessary, and maybe do something to encourage killing them - improve gil drops, add rare drops that only trash in that dungeon can drop, etc.