Your guild’s overall healing versus damage taken seems pretty steady. So there isn’t any more overall healing that can really be done, any extra healing you do will take away from someone else’s healing. Shamans most of all do really poor when your guilds healing reaches this thresh hold because of our mastery. to increase your healing though you could try to coordinate your healing with the other healers and find a niche. for example, you could focus more on raid healing while your paladins focus tank healing, those kind of things. Also time your CDs apart from one another, HT on top of tranq wont go very far and you might find it more useful to use another time.