KOU Black Gear vs Ksehn (ranger) stat gear

I have been using ranger stat gear for quite awhile now. A big problem is the difficulty to kill Ksehn. As a thief, I am at a distinct disadvantage because I have no ability to heal myself. I would guess it takes me about 8 rounds to kill him, and that means landing at least half of my backstabs, something that is especially tough with him.

With 1500 block, KoU is actually easy to kill now. I never thought I'd be able to say that. I have him bleeding after one round, then most often I end up killing him with my hp at about 1000 in the second round. I finally solved the... quest, if that's the right word for it, to get the piece you have to find to get to KoU, so my big concern now is this: do I use KoU black gear or ranger stat gear?

Black gear is black boots (shimmering) and the black plate for me. I don't use the black shield because Irongrip's shield is a light source. This is another toss up for me, do I use Irongrip's for both my shield and light source and just deal with the lower defense, or use the black shield and carry a light source. I believe the weight of the black shield and light source makes up for any extra weight the Irongrip weighs. Stat gear is jerkin of the raven, boots of the fox, gloves of the bear, and armour of the ox.

Black gear has significantly higher defensive value than does stat gear. When combatting cammy guards, VoL mobs, etc, I don't lose near the hp that I do while wearing ranger stat gear. However, this defensive bonus does not seem to matter against big mobs like Savendra, Kehlgarand, and mobs of that level. For mobs like that, the stat bonus ranger gear gives seems to allow you to last longer while combatting them. Any mobs under that level though, such as KoU himself, guardian of the ancients, old crazy man (banana), I can last longer wearing black gear while fighting them.

I imagine my best bet is some sort of combination of the two, but that would mean killing both ranger and KoU, a stout task for a thief. Unless I have 6 hours or more to play, going after ranger sometimes just isn't worthwhile. And after playing a few days with KoU gear, I actually think the defense bonus for just doing exp'ing and stab runs is better than the stat bonus from ranger. Of course this is all a work in progress.