I'm playing a level 55 dark elf vampire lord assassin on the Xbox. I haven't needed to use shadow warrior perk much lately but I found out yesterday that it seemed to have stop working. I used to be able to shadow warrior and insta kill (x30 damage) to the targets face. I can't even do it to a paralyzed victim anymore. I don't know if I broke it or I'm all of a sudden doing something wrong.

1. I did Google searches and there are many threads but not many leading to what I need to know. I did run across someone saying that stage 4 vampirism can break sneak, and I hit stage 4 quite a few times. Supposedly sneak goes beyond 100% and rolls over ending up giving you a 0%. I haven't had much issue with sneak itself but I have found myself to be more easily detected. I have muffle boots, +40% sneak necklace and +25% vampire bonus.

Also I've never really played with magic, so this is my first toon with it, but I've noticed that my invisibility is broken during combat. I can be invisible yet the aggro target will still hit and damage me and continue to follow as if I wasn't invisible. Otherwise, I haven't found other information or complaints about vampirism breaking sneak.

2. Recently I cured vampirism to have access to the face changer and then had Harkon turn me back into a VL. I don't know if that may have broken anything. I thought about curing vampirism again and having Serana turn me.

3. I also recently acquired Harkon's sword (Dawnguard content). I normally rolled with 2 daggers but I recently started to use Harkon's sword. I would main hand the sword and off hand the dagger. I'm not sure if shadow warrior only works with daggers? I tested and went back with dual wielding 2 daggers and the success rate seems to have increased. I also recently started the use of daedric daggers. I thought maybe the speed of the daedric dagger did not work optimally with shadow warrior but I tested that as well. I used a 2.5 speed dagger in my off hand and Harkon's sword in my main hand. I could not pull off a shadow warrior kill at all. I then go back to using 2 daedric daggers and the rate greatly increased but not sure if it's back to normal.

4. Shadow warrior does not seem to work on dragons, animals and high level Draugr, even if something is tanking for me. I used to be able to do it to at least dragons on my other toon. I stopped playing Skyrim for a few months so I didn't keep up with patch notes in between.

Is something broke? Am I strictly forced to using daggers?

I have no idea what could be wrong here...I used shadow warrior successfully with the latest patch not long ago, and sneak attacked a dragon that had landed with a bound sword. Not sure what could be happening to your game...

What weapons do you use?

I'd guess it's the sneak enchants.
Take them off, just in case (though keep muffle) - there are a few skills that break if your perks/enchants exceed 100%...

If not then no clue!

-HK