With your shammies, you can make an excellent flag retriever. It doesn't matter how many they have escorting the FC, just target the FC and Flame Shock/Elemental Mastery/Lavaburst. Most people that play battlegrounds won't react fast enough to heal through that much insta damage, and you can then click on the flag like a madman to return it. The only problem with WSG is you're going to get blamed when you lose, no matter how many flags you return or how high you are on the damage charts.