I will give you the benefit of the doubt and say that you are 45. FM is my main (for now)
1) Spam impact until it connects, yes they OCCASIONALLY dodge it. However its free, spam it like the button is going to break.
2) Your fire dragon, properly specced, rarely ever gets dodged, plus it can stun, plus it can knock back. I has a nice AoE so you dont have to be super accurate with it.
3) Look at your defensive skills carefully, some of them will drop ice debuffs if a SIN is to close. In gerenal i do a great job of fakin most melees into getting trapped by my defensive skills.
4) Get more out of your AoE .. Firewall needs no targeting, and you can stand on it. Your fire tab will get most sins no problem.
5) Lastly, and this is the one thing I have used the most, that has won me 80% of my Blade And Soul Gold. Positioning. Most people are eager to go pound for pound in the middle of the arena. Stop it, you are not melee. Stick to the sides. Its harder to flank and dash around you when you are up against the wall. If they do get around you then impact will make people suffer as they get knocked around by your corner game. This will work on BM and KFM too who are too reliant on flanking (Mostly silvers.)