1) I'm pretty sure the level cap for Guild Wars was made to abolish any sort of grinding. If you just go through the primary quests and missions, you'll definitely get to level 20.
2) A build is a collection of 8 skills that are supposed to synergize in some way. Talents in WoW are almost identical to Attributes in Guild Wars. Each profession has 4-5 attributes. You use attribute points to higher these attributes, which, in turn, make related skills, weapons, and special effects of that attribute more powerful.
3) No class is really WAY better than another. My friend plays WoW and says that Rogues and Hunters are considered uber nubs. This is not the case in GW. All classes are somewhat balanced. You need strategy to compile a build. Then, you need skill to use the build to maximum effectiveness. Rangers are pretty good due to the fact that they can deal good damage, spread conditions, protect themselves to an extent, and have pets.
4) GW is an instanced game. This means that when you enter an area, the game makes a private copy of the area for you and your party. Yes, you can see your party when you enter a new area. This kind of play has its pros and its cons, but I don't want to create an argument here, so I'll leave that for you.
5) WoW has made you hate spell damage classes because your only experience of them is pressing buttons and grinding. About a class that you describe as "a leader of a group and like a armor tank that can heal himself and take on many monsters and ppl in pvp,"
THERE IS NO SUCH THING. What a horrible imbalance that would create, eh? An indestructible class... whew... Here are some classes you may be interested in:
Warrior: Highest armor in the game (80 and a little extra vs physical). Can wield swords, axes, and hammers. Is a viable tank. Has some potent healing skills. Equivalent to a Warrior in WoW.
Ranger: 70 armor with an extra 30 armor towards elemental damage. Wields bows. Condition applier. Mild survivability. AKA Hunter.
Dervish: My personal favorite class. Wields a scythe and wears magical robes and a hood. A scythe has the highest damage range of any weapon in Guild Wars. Has extremely powerful self-heals. 70 armor. Only available in Nightfall, though.
By the way, if you're a first-time player, Factions
IS NOT the game for you. Try and buy Nightfall or Prophecies. Factions is a bit difficult and short-storied.
Also, GuildWiki is your friend.
http://gw.gamewikis.org/wiki/Main_Page
All the information you'll ever need is located there.
I hope this helped, my hand is starting to hurt.
~Polynikes