Yes WW for at least 1 sec i would even make it 2-3 sec.
But the thing is he wont be starting to ww unless hes almost sure it s gonna hit and if he doesnt you firewall right away ? If your lucky you will burn him a little but it wont kill him and hes gonna be so close that it wont be long you will be down. So you teleport and firewall ? By the time your done casting the chance to deal damage to the barb is over he is already back on your tail. I also see many barb use Teleport amulet and that would render hiding behind firewall quite useless. Now with the new rune word there not even need of a tele amulet.