for pve.. anything goes.. pvp.. its a different story honestly.. Racials do play a big role or even sometimes ground breaking role in pvp.. if used wisely.

Example.. a worgen free dash can make or break you in pvp..while it would do nuts in pve.. most of the time.

Another example.. stoneform for dwarfs.. i killed a feral druid because of this ability.. it took of all his bleads and i killed him..so i lived another day cause of this