Took on a Draugr Death Overlord when I was level 7. I had a companion with me who had managed to get himself infected with werewolfiness, so he transformed and took on the Draugr Death Overlord.
It took about three seconds for the Draugr to take him to 0 health, even with the OP werewolf knockback attacks. I panicked and backpedaled a little bit - i needed to leave, but the only way out was through more Draugr, and encountering a horde of multiple enemies is doom with the mod "Duel".
So, I figure, I've got to kill the DDO somehow. Provided I dodge its Icy Spear (50 damage, 50 stamina damage), and block its strikes with its sword, i will be fine.
It opens with all three words of Frost Breath. FO... KRAH DIIN!
Bloody heck. The initial shockwave carves 50hp off me, then drains 35 more from the chilling effects. My character is so slowed down I can't really avoid the next strike, but I can try and block it. I have stamina left, but not much. Probably enough to block a sword strike but be staggered by the strike. (Duel makes blocking more like dark souls - successfully blocking a hit takes stamina, you can still block a hit if it consumes more than your remaining stamina, but it will stagger you, just as in Dark Souls).
I take the hit, am staggered, and hurriedly open the menu to heal. Quaff my potions, shove my mouth full of food, drink some stamina potions, and prepare for the next barrage while waiting for my companion to get up off the ground, still in werewolf form.
The Draugr Death Overlord summons a Frost Atronach, which... fails to get through the doorway. It's too tall. I laugh, then pull out the Eye of Melka, and spam its fireballs until i'm out of charge, recharge it using two soul gems, then spam again. Frost Atronach is dead, the Draugr is barely injured.
I see the Draugr charge up an Icy Spear, and try to dodge - it clips my character, hitting her for 50 hp. Nothing too serious - although i'm a low level, i have 160hp.
The Draugr charges in, I take the hit on my shield, and press the Draugr right back. I use up all my stamina power attacking the crap out of it, staggering it lightly while it takes a particularly heavy hit (in Duel, weapon damage is ramped up, while blocking is more effective. Taking a strong hit, will stagger the opponent very briefly, during which time they're vulnerable to extra damage.)
I capitalise on this split second of stagger, and attack as fast as I can, dealing some pretty major damage instead of the scratch damage I was dealing before. My companion finally gets up off the ground, as a werewolf, then transforms back into a human, and goes into the 'on all fours' injured animation. Useless sack of crap.
The Draugr summons another Frost Atronach, and I promptly flee back through the doorway. My companion limps after me, trying to catch up, and the Draugr chases me down. I block a power attack, take a hefty amount of damage through it, then try and press the opening from the Draugr's slow power attack animation.
It works. The Draugr is stunned momentarily, which lets me deal extra damage again, which is enough to kill it! My companion finally gets up off the ground, and comments something about the Arena, or somesuchshit.
What an exhilarating battle that was.
TES5: Skyrim, running the Duel Combat Reloaded mod. It ramps up damage, makes shields more effective, and costs stamina to block a hit. Enemy AI is also improved to capitalise on numbers, and fight more cautiously, blocking more often.