Idk what ilvl your mage is since you’re posting on shaman and I don’t know what key level you are doing, but the damage you are talking about is normal from what I’ve seen at less than really high level (10+) keys for mages.
I’m far from great on mine, but I’ve followed the guides in depth enough to at least know what I should be doing. However, I got so sick of just doing absolute dogwater damage at lower ilvls that I switched to my hunter for pushing keys. Fire mage is just miserable for me to play and if it wasn’t for my guild not having one to play in raids, I would drop this character.
All that being said, I’m at 662 ilvl on my mage now, running around +8s and doing 2m is a really good run for this char. My hunter, who is now 667 hasn’t been below 2m in a long time and easily pushes 3m when running +10s as MM. (all this as pug, not really organized runs).
I know fire mage really pumps at higher gear levels on players that know it really well, but it really drags at lower gear and it’s a lot less forgiving than frost for a lot of it.
+1 on the recommendation for Preheat on learning the spec. If you really want to play this spec, then you’ll want to follow the advice there closely.