This would be a problem if you actually killed him this many times.
2600 kills is a pretty serious claim so I clicked on your guild to see how many characters were in it then I checked their raid history to see how many kills you have on each of your “Winter” named toons. There are 7 so I’m assuming your other 3 are Alliance or not in this guild.
Winterknight - 32 kills
Wintershaman - 25 kills
Winterdemon - 15 kills
Darkwhispers - 12 kills
Winterdragon - 2 kills
Wintermagic - 21 kills
Second Winterknight - 14 kills
My count comes to 121, which is a far cry from 2600. So until you whip out 3 more characters (since you said you were doing this on 10) with 800 kills each on them, then I going with you are not being truthful at all.