On the last Kronos, we had a dedicated Moonkin player in the guild and because of the fact that he put more effort into his character than many other players, he actually did pretty well in the damage meters. But under neutral circumstances a balance druid can not compete with pure dps classes like Mages, Warlocks, Warriors or Rogues.
As Kruto says, if you want to do at least "decent" as a Moonkin, you have to be packed with loads of mana potions, demonic runes at best as well, mageblood potions and all stuff that increases your spelldmg because else, you're gonna find yourself in the bottom quarter of the damagemeters.
The fact that your +3 % spellcrit aura only applies to your group instead of the whole raid, doesnt bring much benefit to the raid dps. Another dedicated player playing Mage or Warlock probably adds up more to the raid dps than what the moonkin aura brings you.
Anyway, finding a guild that accepts one balance druid shouldnt be too hard. All raid content of vanilla wow can easily be defeated while having a balance druid in the raid, there is no real need to min-max things.
