This is so true. I know I am a very good healer. Everyone says so. I get compliments from pug tanks. I get the question asked a lot "Are you sure this is heroic?" However, whenever my guild leader is in a group with me I turn into this epic noob tard! He makes me nervous bc I feel like I have to impress him and my healing ends up going to crap. So, confidence is key. Once you learn fights it gets even easier bc you know exactly what kind of dmg to expect!.
Specific advice to OP: The in game auras seem perfectly sufficient in my opinion. I mean, unless you are staring at your action bars (bad idea in general) it is kind of hard to miss a giant green leafy icon surrounding your character and pulsating. Also, the sound it makes I always know even if I had my eyes closed exactly what it sounds like when OOC procs. Healing Touch is a druids "Oh shit" ability. HT and "spam" should never be used in the same sentence basically. Tree form is only on a 3 min cd and if you spec into it lasts 10 seconds longer. When there is large raid dmg I Rej/swiftmend the tank real quick, pop into tree, and Lifebloom two to three stacks on all the raid. It is a very efficient heal, much more so than Rej. If tree form is on CD then you'll have to make due with Wild Growth, a Rej/Swiftmend if it's up on someone, and hope they are smart enough to stack in the good shiny green area! Hope this helped.