Castellax price increase was to be expected. They were a bit too points efficient especially when coupled with a Praevian thus gaining Legion Astartes Rules, such as RG Praevian and Castellax gaining Infiltrate and fleet.
My main draw for the Admech is Big Stompy Robots.
And while you can reasonably fit 5+ Thanatars into a 2.5k Lists (Which I plan on doing ), My main question would be: How to make best use of a Domitar?
Do you take the one and give it Paragon Of Metal, like I plan on doing would have T7, 4W, IWND, +D3 HoW, Rampage and 4 attacks base with S10 Concussive at I3.
Or, do you take them in Squads of 3+? At 175 Each before upgrades, they aren't cheap and being CC Focused Beasts with only a Missile Launcher (at BS3 with a Flakk Missile option) means the more you pump into them, the more they're likely to become Fire Magnets and the Larger their Footprint becomes too (We have no model but I'm assuming Castellax Size).
To me, they're meant to hunt other MCs -- admech or otherwise -- or small, Elite Units.
Also: Enhanced Targeting Array: Always Take it where possible or on a unit-per-unit basis?
I'd say for units like Thanatars, +1BS and -1Cover (Which they have to re-roll if successful due to Plasma Wave) is worth it every time due to its S8 Ap2 Ordnance 1 Barrage Large Blast, Plasma Mortar Shot.
Since I'm planning on Thagmata Omnissiah (unless I get the Red Admech Book and makes Legio Cybernetica a bit more worthwhile), Gotta take these or Adsecularis as troops. And I prefer the Stompy Robots
Since they're Jetpack Troops which gun would be the best option to go with their Lightning Guns? I'm of the mind that the Phased Plasma-Fusil would be the best choice due to similar-ish range, S6 Ap3 and Salvo 2/3.
I'm planning on running the following:
Now, Granted, this was made prior to the points adjustments of the Admech Redbook so some shifting will have to occur.
And while, yes, 300+ Points into an Archmagos is pretty silly, its my kind of silly
With the changes to the Magos' being able to join units of MC's I'd be able to park the Dominus in a unit of Thanatars in the backfield and just plink away with his Conversion Beamer while granting the 12" (no 24"?) Cortex Controller Bubble to them.