Might be true when your just starting the game and dont have many items, but with half-decent gear, you can do lot better than 5k.And for your information, Meteorb generally has about 5k fireball damage, and pure fireball non-ES sorc has perhaps 14-16k, or 20k+ with skillers. It all depends on whether 105 or 200 FCR, or ES or not.
What gear are you using? I really can't imagine a meteorb MF getting that high of a damage, although my setup lacked a torch, anni, cta, facets and skillers.Might be true when your just starting the game and dont have many items, but with half-decent gear, you can do lot better than 5k.
My current Meteorb MFer has fireball damage 11-12k, plus -20% to enemy fire resistance. I could go even higher by adding two sojs, two fire facets and couple more skillers, but that would start to hurt my mf, besides I dont really think you even need that high damage if your only mfing.