I'm in a not too dissimilar position with similar weapons, but I'm missing the nice T5 one you have =P. I'm looking at getting Brutilizer and whacking on a executioner enchant as a pure threat weapon, and replacement for a similar enchanted KD.
I recently got UW and put mongoose on it as an avoidance (my QBOTP didn't have much tanky stats even with a mongoose) / mitigation weapon. The only downside is like with QBOTP I'm not impressed with the threat off it, even with the extra damage. From tanking Father Winterchill it seemed a significant reduction by a couple of hundred. What I have started to do is use my regular KD and build up decent threat, if I start to need to use pots & panic buttons then I'll swap the UW in, which seems to work fairly well, especially if I maintain a good 10K lead on threat.
I do have a hunch though that if/when I get a chance to mug Supremus I won't use UW much and the advantage of a pure threat weapon, and fact you can improve stats elsewhere makes better sense (dead MoFo's can't cause damage...), or until I get beaten to a pulp.
Former TBC/LK Tank
Waiting for Dunmail Jnr to sleep to enable online gaming.