I’m not sure if anyone has pointed this out, and perhaps it is because other’s playstyles are not similar. There is a bug when you are casting in place as a Necro with Simulacrums in which when Simulacrums are hit by Elites and Bosses with knockback attacks, they will often get knocked into an above area, something resembling the ceiling of the map. Sometimes if a wall is near, they will get knocked behind walls. When the simulacrums are in these areas, None of their attacks hit.
Now it is a given that with the new HV, the simulacrum(s) will teleport to you when you move. This is a quick fix to reset them and continue having them deal out damage alongside you. The issue is that depending on your build, playstyle and situationally speaking, moving in certain instances can heavily reduce your DPS. The same can be said for when you are in place ready to unleash some attacks and you do, but in that instance or maybe just before, your simulacrum has been knocked into outer space where it cannot hurt any mobs.
I am not sure if this is an issue which has been mentioned or addressed previously. I feel it is a good time to bring it up considering the upcoming patch. It is easy to notice and quite problematic. If the simulacrums just got knocked back into other playable areas where their attacks still hit mobs, that would be alright and it would be the natural and bug free fix. That is not what often happens unfortunately, so my request is that perhaps it could be addressed in the upcoming patches, especially considering the focus on use of simulacrums with Necro.
Edit: Posting again to update with more information about the bugs with simulacrum.
(Sometimes) when teleporting, simulacrums do not also teleport instantly. If you teleport and immediately start attacking, the simulacrums may remain in the previous position and continue attacking there instead. This is potentially problematic in the case of AOE abilities being used (Death Nova) as they will not hit intended targets. For simulacrums to teleport to correct positioning, the character must either remain in place long enough or actually move around not by teleport, but by walking.
Also, there are instances in which the Simulacrum will completely disappear while the skill remains active as if it is still there while simultaneously since it is no longer actually there it is not dealing any damage. You can move through the map but it will never reappear next to you. This happens when using constant healing abilities, such as cursed form which provides leech curse. There is an issue with the simulacrums “dying” but also not because they do not benefit correctly from healing.