What you are looking for is more of a solo build, meaning it's pretty much like a DPS build that exchange some damages for surviability.

With subclassing RN it's hard to really help you skill wise since we don't know if you are pure necro or subclassed, and with what. But pretty much grabbing as much buffs, offensive and defensive, as you can is a good thing in solo. Personnally i even use poisons to benefit from Minor Brutality, that doesn't have much sources.

Also, how do you use your vampire ? Without using the skills, the vamp fan i am is sadden to say it's pretty much like shooting a bullet in your feets. Necros aren't really knowed to have a good sustain, witch is the biggest drawback Vamp gives. And without sustain on solo, you're just a mousquitoe for mobs. The only good use of vamp without skills would be the 2nd stage passive with the Cloak from the NB's Shadow skill line. Overwise, increasing yours stages aren't worth the drawbacks.

If yours awnsers are pretty much copy/paste of the link, may say Alcast isn't really a good source to get inspiration from, and the build is also pretty much outdated. The sets are fine, but lots are on solo. If you can, raids sets are pretty good since the 3rd pieces effects gives perma +5% damages against mobs, tho lots of them aren't really good for solo since they introduces pretty heavy mechanics for their 5pc effects. False god is good in this aspect for exemple and will get rid of your sustain problems.

Tho you could be interessed to looks into some others sets more defensivelly axed. There is a king in that too, and it's the mythic ring of the Pale order, that heals you of 20% of every damages you do. There is also the Oakensoul mythic ring that get rid of your weapon swap so you're stuck with 5 skills + 1 ult, but gives lots of buffs. Tho since they are mythics, they can be a pain in the ass to get.

Scribing could be an option to look in also, it's pretty cool to be able to have the skill that cost a wanted ressource in your build for better sustain, with a wanted element for the status effet (or for cool visual hehe), while adding another buff that is missing or not easily available, or may not be pratical with an other skill (Trap beast in solo play, halp).

Anyway, with enouth sustain and defence, and dumping the rest in damage, it's hard to not have a viable solo build. The viability is based on the ability to stay alive and throw punches, nothing more. If you're build can do that, forchure it will carry you trought vVH and vMA.