Guild Wars 2

I have got hit by flame blast this morning in WvW for 2x 4500 dmg and I thought how. So I test it on mobs and found out that if you let it go all the way it explode from original skill and then from new added skill too. So you hit with the explosion 2 times.

On the picture you can see dmg from rolling through the mob and then 2 dmg from explosion.