I've played since release and to answer your questions:
Combat: The combat is okay, it's clearly made around PvP which makes leveling extremely boring. (However it's fast and can easily be done in 2-3 days). Most classes have high mobility and interesting combos you can preform. Once you get to higher levels it's really enjoyable and some of the fights start to get rather hard.
Loot: Loot is basic as fuck. You get coinpurses and a chance for a gear drop. Coinpurses contains money and sometimes Archeum which is used for crafting.
Quests: Same quests over and over until 50. Kill 5/8/12 of or use this/pickup that.
Story: There story is okay I guess? In comparison to WoW the game has 0 lore, it has some interesting backstory which is unveiled in the starting parts of the game.
Gameplay: The game feels really smooth but has high requirements for you to run it at good graphic settings. Some areas of the game is absolutely gorgeous tho.
Endgame: Dungeons, PvP and crafting. There is a lot to do before and after you hit 50.
PvP/Balance: The game is balanced, but it takes a lot of skill to be good at and you have to invest tons of time into getting gear to even be viable. It's a grindfest.
F2P Model: You can play F2P without any issues while leveling up, however once you hit 50 you might want to invest in Patron (Monthly sub). This can be bought with in game gold which is easily farmed through grinding, farming etc.
8,9 GB Download I believe and tons of active players.
I'd say give it a shot, but you have to be prepared for the massive grind. Being ganked by higher levels constantly once you enter PvP zones. The game isn't that straigt forward and there is a lot you have to research on your own to understand certain aspects of the game. You need lots of time to invest into the game to be good at it or even be viable for endgame PvP. However alot of the community is great and there are many guilds that will help you along your adventure.