This might be silly, but I just wanted to share a few tips/tricks for Necromancer that I only caught later on that helped my DPS and survivability. I'm someone that played at launch and didn't play again until last season (Pally, which sucked)
Before some of these realizations, T12 felt very uncomfortable to run. Now I can breeze through it. Also, sometimes I feel like the guides touch on things but don't fully explain certain key things as they should be explained. Hopefully at least one person will read this and be like "ahh that makes sense"
- Cult Leader - 100% attack speed is like one of the biggest priorities. The best way to get it easily is to have your golum run Gargantua. Pact of Bone also helps if your golum isn't very highly leveled, but eventually the golum provides >100% by itself.
- Breeches of the Blood Moon - This unique allows your minions to cast iron maiden and decreptify even when it's not on the skill bar. Put at least 4 points into each skill though, 1 for the initial and then the 3 abilities for it. This SIGNIFICANTLY helps with survivability and DPS. I did not have any points into it before, but after adding it I get healed rapidly and always have maxed stacks of resolve (which helps me not get one shotted anymore), ferocity, and overpower (ferocity and overpower combined adds noticeable DPS increase). Main reason why T12 is easy breezy now.
- Blight - I saw a lot of builds always say to use blight and never explain why. Blight 1) pulls in enemies around the target hit so your minions can hit them all at once and 2) chills them, proccing Bloodless Scream at first hit from minions. I was using dark corpse explosion before this.
- Death Grips vs Hand of Naz - Both do very well and excel at different things. Hand of Naz is better for clearing mobs but single DPS belongs to death grips. Have a pair of both on you and switch when needed.
- Skeletal Priest - Skeletal Priest on the Skeletal Warriors branch is nice when not using a corpse-utilizing skill as it auto-casts every 8-ish seconds, so you can have that corpse paragon node running all the time. Might not be worth the DPS drop from missing 3 skellies but I am lazy.
- I enjoy using Will of Rathma as my unique charm. I think it's basically a flat 40%x dps increase and triggers off almost any status on the enemy. Most guides don't mention it but I appreciate it's simplicity
Please feel free to add others in the comments!