If you think paladins are hell for mages, then gl against shamans, they are true cancer.
 
 
	No, if you want to achieve a high pvp rank, then ofcourse you will need a premade but there will be good premades on alliance and aswell on horde side.
 
	In matters of PVE. Gnome will probably do most dmg, because of his racials but the smoothest experience does not has to do much for what faction or race you will decide, it´s more about the community you will play with. Search for a nice guild which fits to you and you will have a nice experience anyways no matter whether you play horde or alliance.