I didn't find any of the bosses of UK or Nexis dropping anything of interesting to my well semi-well geared shaman.
I thought the quest rewards for having done something in the instances to be much more interesting.

you can clear all of the trash in the Nexus and never have to kill any boss. they are all optional.
there is really only one boss that needs to be killed in the Nexus to get the quest reward and that is Anomalus.
Quest: Postponing the Inevitable
I'm not 100% sure you have to kill Anomalus to finish this quest, but I stood in the spot behind where he stands to finish the quest.
for some reason I found Anomalus hard to do although my follow mboxer in my guild found him quite easy. ( no pictures so I'm not sure I believe him )

the boss that needs to be killed in UK is Ingvar the Plunderer and I hated him.
I had mana issues in UK tring to get the quest reward there, I had no problem killing the Plunderer the first time but it usually took 65% of my mana so when he rezed I would wipe every time. I'm going back with some mana pots to try that again.