this is something you wanna have up to level 30:
http://db.vanillagaming.org/?talent#hZxVbdV0z
shield, a least 1vsworld leveling , is not an option because shaman kill veryslowly compared to many classes. you got no special attacks with weapons, only via spells. At low levels if you force yourself to cast, after few of them you're oomm. 2handed weapon solve this problem. Higher maximal dmg and improved SOTE totem give a nice damage boost. parry increase your survival and in this way you will always have enough mana to heal yourself between pulls.
if you wish to level with shield because you hate your life i suggest something like this for level 30
http://db.vanillagaming.org/?talent#hVZEzf
then at level 40 something like this
http://db.vanillagaming.org/?talent#hVMuZEVf
by level 50/51
http://db.vanillagaming.org/?talent#hVMuZEVf0x0uk