Lets start with the basics. My lists are always evolving, and this list is a last generation list. Means what I will be fielding after the holidays (currently) is refined from this list. It has evolved.
Lets start with the Backfield. The backfield consists of the heavy support choices. Basilisks and Hydra Flak Tanks. These are a reach out and hurt someone style of backfield. Also sitting around are a combined infantry squad and your company command in a chimera.
Hydra Flak Tanks
The hydras are fielded in 3's simply because in order to be efficient (1 armour kill a round) you need three hydras. Destroyed transport Av11. Since you need three pens on average to blow up a vehicle, you need this many hydras. Efficiency is everything. One unit shoots, one dead transport. Of course smoke and other factors limit this, but you can only plan for what you can. Hence two units.
Like any other multi-shot barrage, you have a better chance of hitting where you want to, if you simply have more than one shot. A single basilisk is very inaccurate. With 3 your chances of scattering back to where you want are very high. If you do not believe me, get out your dice and see. Read page 32 BRB if you do not know how multiple barrage weapons work. Basilisks also can fire directly within the minimum range. This is awesome, and means that these workhorses are busy the entire game. Hydras open up the transport, the basilisks destroy whatever comes out. Its a one two punch that reaches the entire board. Protect these by having chimeras or hydras in front of them to give the basilisks cover saves.
This unit is a non moving vendetta. It is deployed in the backfield with a strong field of view. Spread this unit out, and make sure its in cover. If the opponent has first round assault chances with anything that wreck armour, use this unit to spread out and bubble wrap it. (do not give your opponent room to assault through this unit if you are concerned about first round assaults). (scarabs, demolition veterans etc).
The infantry squad is ideal for holding a backfield objective, and is very hard to remove for capture and control, and seize ground games. In seize ground, this unit often holds multiple objectives (my best is claiming 3 objectives with this unit in a tournament game).
Do not forget to attach independent characters before deployment (its a rule). Attach the commissar with a camo cloak to this unit. If under heavy fire, simply go to ground. His stealth special rule applies to the unit, so the entire unit will get a 2+ cover save. Then when it is your turn, order them back up with the commissars leadership with a re-roll with the vox, and return lascannon fire. If not going to ground, give them fire on my target or bring it down for twin linked shooting.
Company Command Squad
These guys are simply there to provide cover and orders. Catch falling back troops with these guys (ordering them back into the fight) and supply your infantry squad with whatever orders they are needing. Your opponent will often go after your CCS, but that is great, let them. They come with a lascannon, so they can help with support fire from the hatch in the chimera.
One trick with Company Command
In a tank crowded field with units falling back, often you simply have to not provide a falling back unit a easy route to your board edge. Its very easy to corral the fleeing unit right towards your Company Command so that they can be regrouped.
That's all I have time for right now. I will continue this after I get some work done.