General theory craft of list.
I am trying to have multiple (as lest 2) units that can handle the same general type of target.
I am mixing in infiltrate/deep striking and reserve units (for the first time). I am trying to achieve 2 things with this. 1st is to, in some why, dictate my opponents target priority allowing my heavy armor and transport vets to get close enough to be of use. 2nd is to create a 2 to 4 sided kill box where I can grind up my opponent.
That sounds well thought. Cross fire is an effect, that is incredibly efficient and deadly.
Lets look at your list:
HQ: Why do you need the vox? You have to disembark the vets to give orders to them. That results in unnecessary counter moves from the opponent. You will change one vet squad for a transport. That is not the idea
So keep in the vehicles and you wont need the vox. I would recommend the standard instead in case your veterans have to bail out. There is nothing worse than a pinned vet squad which has to be ordered to life and therefore still cannot move... And even worse, a retreating vet squad due to explosion damage or something... If you want to go for the
cc with the command, you will need a bodyguard for straken. You have one more model that can soak damage from straken in crucial situation where you have to win combat. If you dont, then I would stick to the normal officer.
Otherwise it looks perfect, the
HQ.
Elite: I would cut first in the psykers. 6+ overseer should be enough to reduce the important
lds to 2 or 3 and wound most targets on 2+.
Marbo is a two sided thing. He is suicide if you want to use him, if the charge fails, he is an easy killpoint, if you hide him, you wasted 65p. If the charge hits, he is still dead afterwards but has at least managed to do something useful. But I think he is too dependent on rolls... I would cut him personally.
Troop: 2x meltavets... personally I dont like meltavets but you need at least one unit to repel attacking tanks. But I would recommend a plasma squad to deal with what comes out of the tank, which is actually more important. Harker with flamers but without chimera? I would take a dedicated chimera and outflank them in it. They are faster and much harder to kill. One special advice: Take demolitions on them. You will get a unit that can deal with terminators, horde and walkers very effectively. That is a very brutal unit.
The platoon is a bit unnecessary here. It keeps the command behind because the
HWT need orders and there is no commissar to keep the infantrysquads standing. Now you will get overrun by a combat squad... How about penal legions? In my army they always outclass the platoon due to their adaptability (scout=scout move or outflank)
Assault: The banewolf... Actually I have no experience with him, but I would suggest he can be efficient if you keep him out of enemy fire and use him to control the enemys movement.
The Valkyrie. My intuition says, you wont need it in that list. I would rather stick to your principles and take a second vendetta for more anti tank long range.
Vendetta. Yep, no brainer.
Support: I would take a second executioner instead of demolisher. 3 small blasts are far better than one large. And vs vehicles you have meltaguns in short range and dettas in long range that should do. You rather lack anti
teq/
meq.
Overall I think it is a good attempt, you just need little finetuning, but I can see a good concept behind it. Speaking of 150p cutting: Cut Marbo, Straken and a few psykers and the Valkyrie, take a chimera for harker and you should be within 1750. You could invest the remaining points in plasmaguns for veterans.
