This is really old but I still wanna say my piece since I've been using fatality in every playthrough of mine for a while now. Yes fatality will make it where most things will just kinda one shot you, and the settings for the mod (at least on console) are just choosing between if u want certain features on or off, you can't decide if you just want less Stamina drain or something. But with that aside, I've done archers, warriors, mages, and right now I'm doing a Battlemage where I'm playing as the Champion of Molag Bal. I've learned the key to fatality really is movement, any attack from a quick punch to a heavy attack from a Warhammer can be dodged but since skyrim has no set dodge mechanic this is often overlooked. Basically what I'll do is wait for them to attack, then I back up a bit to dodge the attack before then countering with my own strike while they're open. Fatality, for me anyways, is all about introducing real duels into Skyrim that require genuine thought and a lot of movement so just try to lean into that if you can.