Oho. Do you think, I'm not able to run away during fulminating?
naive!!
Furthermore, there's another problem with your way of combat.
I guess you'd cast fulminating right after UM; but in this case, 5 seconds of UM have already been elapsed (stopping, casting ...). So, you have to kill the other barbarian within 5 seconds...
And the other barbarian would have the chance to run away much earlier if you want to cast fulminating because you'd to cast UM a few meters before you'd arrive. Your UM is wasted, you don't hit me only one time because I've ran away... My UM is available and so, I'd run forward to you, activate UM right before arriving and I'm able now to knock you down, before you could run away because of the short global CD of UM
I hope, you'll all understand my tactics ...
And no barbarian without feint/kick 4-5 could win against such runaway tactics.
Although being the most effective way to fight other barbarians I do not use such tactics or knock-downs at all because it's simply boring.