Holy carp. So... I just spent ~30 mins killing Gedna Relvel. I guess my problem was being such a high level when I opened the tomb, and therefore, set her level.... I had to lay down my trusty everyday imperial weapon, and pick up the ne'er-before used Chrysamere to get it done. After ~ 30 minutes of continual full-draw blows, she fell dead... but Chrysmere was at a fragile 1378 / 6000 health, and down to 381 / 1140 enchantment remaining. I chugged multiple ~5min restore 100 health/sec potions. I am at 100 difficulty... but holy carp. That could have easily been the toughest duke-em-out of the game in my 8 years of playing Morrowind.
After her health was showing showing no yellow (down to near-zero), it still took 45 more hits. 45. What the heck? I know she had like 5,900 life due to being leveled... but what the heck? Dang. Guess I really earned that notch in my Dragonscale shield....
I also got a kick out of her fisticuffs... every 2 or 3 minutes, she's throw a couple punches, then go right back to spellcasting. I almost laughed out loud a couple times. I think the reflect from Chrysamere might have helped a bit in that fight....