Battle Report: The Disciples of Entropy vs Tyranids

Bonus post! I got to play a couple games recently with the radiation army that I am building. I have taken to calling my army the "Disciples of Entropy" as an analog to the "Children of Atom" from the Fallout series of video games, which is also the inspiration for my army's backstory. I am a little fuzzy on the details of the battles since I did not take good notes, but the overall story is essentially there.

The Armies:

The first battle was against Tyranids and Genestealer Cult allies. The Genestealer Cult allies consisted of two of the "The First Curse" formations, so lots of Genestealers and two Partiarchs. The main Tyranid detachment featured some Zoanthropes, two minimal squads of Genestealers, a Mawloc, a Trygon, an Exocrine, a Tyrannofex, a Lictor, and a Hive Crone. The Warlord was the Death Leaper.

The Disciples of Entropy main detachment is a Skitarii Maniple containing two squads of Vanguard, one with three plasma calivers, one with three arc rifles, one squad of Rangers with three transuranic arquebuses, two Onager Dunecrawlers both with neutron lasers, and one squad of Infiltraitors with the Pater Radium relic. I also took an allied Cult Mechanicus formation: the Cohort Cybernetica, which consists of two units of Kastelan Robots and one Tech-Priest Dominus. I also included an allied formation of Deathwatch: a Dominatus Kill-Team, with Corvus Blackstar dedicated transport. Finally, I took an allied Inquisitorial detachment of just one Ordo Xenos Inquisitor to ride with the Deathwatch in their transport. My warlord for this game was the Tech-Priest Dominus, who rolled the objective-identification trait from the Cult Mechanicus list. I had to substitute my Anvil Industries models that I use as Militarum Tempestus for the Vanguard.

Deployment:

Tyranids set up and went first, with both of our battle lines fairly spread out. The cult ambush deployment didn't result in any first-turn charge potential (thankfully for me), but did allow the 'Stealers to get very close. The mission was The Scouring: six objectives with random VP values.

    

Initial setup before Cult Ambush deployment, then two after Cult Ambush deployment.

The Battle:

Turn one, the Tyranids moved in. doing little shooting and thus little damage to my lines. On my turn, my Skitarii and Kastelan group moved up and laid waste to the center mass of Genestealers. After realizing that the Patriarch has no invulnerable save, it was taken out, too. The Vanguard to my battlefield right took shots at the Tyrannofex, but did little, and the Onager Dunecrawlers did a wound to the Exocrine.

  

The center Genestealers (and upon later realizing it had no invulnerable save, the Patriach) get wiped.

Unfortunately for me, it was at this point that the Tyranids started to lock in a lead. The Death Leaper showed up right behind the Vanguard and Rangers in one of the buildings on my side and managed to kill the Vanguard Alpha with its flesh hooks. The Trygon also arrived on the right flank near my Infiltrators, and a Lictor popped up near the center of the board as well. The First Curse formation on my left flank made a disordered charge on my two Dunecrawlers. One of them did explode and take a bunch of 'Stealers with it, though.

  

The Death Leaper arrives, killing the Vanguard Alpha with its flesh hooks.

The Genestealers and Patriarch assault the Dunecrawlers. One of them explodes, killing a fair number of the buggers.

On my turn, my robots moved up to deal with the Endocrine (which failed a charge the previous turn), Lictor, and the Zoanthropes. My Vanguard tried shooting at the Death Leaper to no avail since they were only allowed snap shots. They then tried charging, which was a complete disaster. The Rangers and other unit of Vanguard ended up taking down the Tyrannofex and the Robots dealt with the Exocrine and Lictor, while the second Dunecrawler succumbed to the Genestealers.

The Death Leaper disaster.

This is where both my documentation and recollection of events becomes a bit hazy, but somewhere in the course of the battle, there was a disastrous charge by the Infiltrators to the Trygon, and the Rangers were taken down by the Death Leaper. My Deathwatch reserves did eventually arrive, intending to deal with the Death Leaper or the Zoanthropes. The Mawloc, however, took care of them instead. The Kastelans killed the Mawloc, but by that point they were all I had left, so I ceded victory.

The Deathwatch arrive, and just as swiftly depart thanks to the Mawloc and Death Leaper.

Conclusions: 

• I should have known better than to spread out so much, especially against the Genestealer Cult and their Cult Ambush deployment. I probably should have placed the Dunecrawlers in the center with the Kastelan Robots. 
• The Kastelan Robots are a far tougher model than I am used to, and they were absolute tanks. The only trouble is that they still only move 6", so to avoid having them just wander around the board the whole game, they need to be in the center as well, especially with so many reserves coming in from my opponent. I would like to use them as a flank guard, but at 515 points for the unit, that would mean a large part of my army could be avoided. I think they will simply need to be moved up straight into enemy lines to provide an irresistible and frightening primary target while the rest of the army moves around them. 
• I think I misused my Deathwatch here, and they should have stayed inside their transport to get a more optimal charge. They came in a little late to make much difference, but still.
• Not exactly sure how to deal with units like the Death Leaper that can arrive in the midst of my battle lines and almost necessitate close combat to deal with since getting shooting hits on them is very difficult. We did a final fight between it and the Kastelan unit, and the robots were able to take care of  the super-lictor just fine. However, I can't keep the Kastelans in my back lines to guard against such things since they don't have great shooting and I would thus not be using a quarter of my army's points very effectively.

I played another game that same day, and that will go up as another battle report very soon!

What is the best way to deal with infiltrating/deep-striking/pop-up backline units? What do you think I could have done differently? Leave a comment!

EDIT: I have since come to realize that due to me thinking the Kastelan Robot maniples were 190 points each, when in reality they are 290 points each, my army was overpowered for this game! Sorry Tyranids!