One important thing you need to remember is that as a SMN you are not only dishing out loads of damage (probably too much to be honest), but you are also a great supporter. While your heals are not very powerful, they are still helpful to help out if one of your healers is down/oom/chained/whatever. Your heal is potent enough to quickly top you off after aoe nukes, making the lives of your healers much easier. Level up your thaumaturge until you get swiftcast, and instant battle rez your way out of wipes. Don't forget Virus, and even Trisaster can sometimes prevent wipes if your tank isn't an idiot.

I have prevented wipes countless times with battle rezzes and heal support (heals getting kicked from platform by titan, or lagging etc). It's not all about the damage with your class, you're not a black mage. Of course your support will become weaker when you hit a certain content level, but do never forget what you can do (did i mention instant battle rezzes?)