Hey zxcvbnb,
first off, welcome to the Forums 🙂
@Volin made a guide on Fire/shadow for rPvE a while back:
It is still reasonably up to date, but was written before Wasteland Terror and Banzai Lord were in the game.
Since you want to run Bloodhorn, I guess Banzai Lord is not really what you want, since this a different kind of deck.
To be honest, I have not really tried out a lot of Wasteland Terror yet, so I can not say, whether it is a good replacement for Disenchant.
Shadow T1 is very solid and allows for early Resource Boosters. Since you want to play mainly rPvE 10, you should consider Shadow Phoenix in T2, since it is usually the more reliable option than Harvester. If you play them, make sure to combine them with Embalmer's Shrine though!
What you definitely need is some form of healing/sustain. Life Weaving is already a good start, but you do not have a strong heal yet. I personally like the combo of Undead Army + Bloodhealing, which can give tons of healing to your Bloodhorn. The Undead Army also synergizes very well with Unity (especially the blue affinity).
Also, consider replacing Unholy Power with Unholy Hero since it scales much better into the late game and Life Weaving is typically enough at the T2 stage.
I would highly recommend to get at least one upgrade on your Soul Splicer, since this allows you to collect corpses from far away. Infect Upgrades are also really good, since they can give you even more crawlers.
Other than that you got a really solid base. I hope those tips are helpful to you 🙂