I imagine you can string out the Plague Drones as far as you need to for the salower Heralds, then whenever you make an assault you slingshot the Heralds back to the heart of the combat with pile in moves. The list is a dual deathstar (or even triple, though one Screamer unit won't get Grimoire, if you roll well enough on HoT powers) of sorts, and it's placed pretty highly in tourneys lately: Screamerstar plus Dronestar, buffed, massaged and tweaked by Fateweaver where necessary. It'll dominate the psychic phase, has good mobility, and it has the option to branch out into summoning to cover ground and objectives--but isn't invested in MSU if kill points rear their ugly head.
I imagine it would struggle pretty hard against the newly released MSU Space Marine competitive lists, though--I dunno if it would be able to spawn summoned squads fast enough to counteract all that ObSec, or have enough anti-tank to clear all those Razorbacks/Drop Pods.
I haven't heard about how competitive the AdMech are, but you may be able to proxy Guard as them to a degree. Sentinels as Ballistarii, Kasrkin (or even guardsmen) as Skitarii, etc. They seem like quite the glass cannon (except for the Kataphron and the Kastellan units), but may well be worth it--especially that formation where every single unit upgrade you buy is free.
What sphinx of plascrete and adamantium bashed open their skulls and ate up their brains and imagination? Imperator! Imperator!