ive solod hh quite a few times now and have figured out a few thing that may help others out.
first of all, it can be stealthed pretty easily (no rog skills reqd) and quickly once you know it well. im not gonna get specific, but the xp/min on the basic quest version is pretty high. if you have 2 men, one for each crest/side its even faster. devious bonus.is possible.
its also possible to go devious and still get all the keys you need.
on the door/floor dropout trap if you dont have a pet, you can survive it be standing far away from door and quickly doing a one eighty as you fall fo grab edge behind you. if you do this a group people will be impressed.
you can solo stealth pull the spear from the skellie boss, just have to find right spot, front left works best for.me.
on extended version, if you go ahead and open door near kobold area that later leads to the chest where floor drops out you can just invis right to it later, nothing follows when you drop.
when fighting white dragon do not backup after you . first activate him(my default action) or you may be killed by the rubble falling, theres no save, think autodeath.
thats all i . can think of, feel free to add.more in thread.