The first and foremost is some sort of an aiming or targeting system. I play a sorcerer, and there are times where I'll cast, and my toon just won't turn to face the target, whether I click on it, turn to it's general direction, or not. I understand that the game's attack system (seems to be) is intentionally designed so that you can step, run, and jump out the way of enemy attacks, and is especially vital in taking down those with ranged moves. However, if there was a mechanic implemented, perhaps a "highlight", where you mouse over the target and also hit an easy to reach/natural button before clicking, like say tab or some such, your character will turn to face that immediate direction and attack at the same time, so there's no attacking in the wrong direction while trying to situate yourself. This is just an idea to not break the game's original design, and make it more seamless as well as less aggravating to attack enemies, especially with ranged moves. While it's not hard to take a moment to turn and face, but while you're running around avoiding taking those hits, sometimes you just don't attack the way you would like. I do it often, and I've seen a few others do it as well.
The second mechanic that comes to my mind is the aerial attacks. Again, this is more for the ranged mechanic, rather than the melee, but I could see it working for and benefiting both. The aerial attacks are pretty nifty. I picked up some rank 3 gear last night and noticed my air attack changed from the pound, to a charged punch to the ground resulting in a weak AoE attack. While it's cool, I don't find it rather useful at all. I'm not sure how other classes fare; but I know pre-faction and Venture (rank 1 buccaneer) both have insignificant aerial moves as well. A little buff to the damage (not too much, like +0.7), and for classes with ranged attacks as their basic attack, they should be able to use that move from the air. As a sorcerer, I should be able to jump and throw a bolt of lightning from my wand. I'm sure other ranged users would like this type of control and maneuverability. Single click for the ranged air, and hold for the original aerial type move, is my suggestion to this.
Third goes out to the size of the zones and the mob mechanics. I've noticed a lot of people complain about kill-stealing, questers getting in the way of farming, and so on. I've also been subject to these things, and have - you guessed it, a suggestion. I suggest that all zones be made significantly larger, giving more space for the several players that come to these zones. With the larger, more open space, you can add a few more spawn areas for mobs, giving players a larger field to hunt on. This will provide enough space for everyone, though it isn't a permanent solution (as there is none), I feel that it's one of the better ways to solve these issues. With extra space, and more monsters, players won't be on top of each other for quest kills and loot.
On a side note, I recently read someone else suggest a mount-type to help with traveling. With the larger zones, having a mount would almost be necessary, if not most convenient.
As for the mob mechanics themselves, the way the aggro to players is kind of frustrating. Their aggro range is short, and for someone like myself who kites them around as a ranged class with little armor, taking that one extra jump outside of their boundary and having them reset is annoying. Also, mobs should be tagged - players constantly attack mobs that aren't theirs, only to not gain any loot and, while it's only a moment, waste their time. After a player hits a mob, it's healthbar should be grayed out for other players, or something of that nature. A mob that I attack should also want to kill me - not some other guy that happened to walk by. I've noticed that if there's two players in proximity to their aggro range, a mob will choose which is closer, rather than which initially triggered the aggro, though I may be wrong about this, I haven't looked into it too extensively.
Well, mods, designers, testers, and fellow LU players, I thank you for your time. These are just merely suggestions of what I perceive will help make LU more enjoyable for everyone, and not just myself.
-Nox`