Warmachines combine well with Legionnairies and Carnifexers, since the former are a long-range nuisance, whereas the other need their enemies to approach to within striking distance. 2 Warmachines + 2 Units would seem like a good idea.
The key to winning in Godslayer is a good eye for synergies and order of activations. Scenarios necessitate a direct confrontation, therefore playing exlusively with artillery will not be too effective. The Technocrat might change that, but some heavy-hitting infantry will still be required to provide a solid counter-punch.
Necromagi support infantry, not Warmachines. The Undead sub-faction used to be though of as overpowered, but after 2-3 games one learns how to approach this matter. The most common, and kind of obvious way, to play the Undead is a lot of minimum Legio Mortum units, amped by Magi, supported by artillery and Carnifexers. The Legio Mortum go to the front, the Magi spam their underlings via summoning, while the Carnifexers take out any larger threats. Basically, one needs a quick and sweeping attack to remove the Legio Mortum (the Imperial Post Office, because they are responsible for dispatching all offensive spells to the enemy). This can all change when the Moloch comes onto the field.
The best way to test is to play, play, play
Advice is one thing, but if you can come up with your own army lists, play them, then give yourself constructive feedback and present it to the public, then you can learn more and your e-interlocutors, too