How to beat ultra hard/impossible AI?

[Onewa]

Greetings fellow Gladiusplayers,

I may have some questions to ask the veterans of this great game. I nearly played now 60 hours of this game and suceeded to beat the very hard AI with every faction. Mostly in 3 FFA or 1vs1. But now I have the feeling I am hitting the wall against the ultra hard AI. I will keep trying to beat the AI, now mostly with Imperial Guard, cause I like them the most. I just hope maybe someone can help me. To better help me I now try to explain my tactic or my way to play until now.
The last four matches I played on a middle 4 FFA map. I started with barracks spamming Imperial Guardsmen, building than tech and teching for grenades, Manufactorum and the building for Settlers. I try to get as many post as I can killing wildlife with superior numbers and reloading if I lose any Squad. Enslavers are killed when I have the anti tank grenades. The AI have superior numbers and better tech so I need Heavy Weapon Squads. When I come to first contact with the AI I have a ♥♥♥♥♥♥♥ of Imperial Guardsmen, 2-3 Sentinels and 2-3 Heavy Weapons Squads and a Commissar. I try than to tech to Imperial Bastion to try to fortify my position. At this time I have 2 cities or three. I made the experience the best way to massacre the AI is to create "Killzones" where the AI gets killed through Overwatch and than retreating rinse-and-repeat. Slowly bleeding out the AI and kill him through superior positions and higher level troops. At some point I can start to push and destroy his cities and push further to victory.
Now that worked fine with the very hard AI after some practice and on 3-Player Maps or Duell Maps. Maybe it just get with the 4-Player Maps together but surviving the early game is now a lot harder. But thats is somewhat managable the thing which really ♥♥♥♥♥♥♥♥♥ me is that sometimes the two AI are fighting me at the same time. So I repelled the ork Invasion it worked out well. And than at the other side the Tau come with ridiculous numbers Krisis "I-One-Hit-Imperial-Guardsmen-in-Cover" Suits and Ghostkeel Suits with Ghost support. Yikes. So hard to kill with range units. So my questions are:

1. Should I just entrench my three cities and wait for Lemans Russes and Tank Commanders? I have the feeling it is worth to fight the wild life and get posts to improve the early economy.
2. How many cities is ideal to play with? Until the T10 loyalty tech, 3 cities seems for me the ideal numbers of cities.
3. Which Edicts should I tech first?
For me the Edict to improve my food productions seems in the early game the most important one. I try to specialise each city for different kind of production so that the Edicts are more potent.
4. Can someone recommend playing IG with tanks only? I have the feeling that without Heavy Weapons Squads the Damage is just missing. Sentinels are okay but deal not enough damage atleast in my experience. Hydras feels somewhat lackluster without Heavy Bolters and Basiliks seems great to damage undamaged units but kinda bad to snipe and finish units (unless when one have 3+ Basiliks). Honestly imo mech IG seems beginning to get strong with the Heavy Bolter tech and Leman Russes and the Tank Commander (Emperor bless his presence). Leman Russes are phanomenal in every sense but the tank commander is so fricking expensive it really take some time. And rushing him only to support some Sentinels dont seem like a godd idea.
5. Are Militarum Tempestus worth it?
They are honestly in every way better than Imperial Guardsmen, but in until now I mostly used Guardsmen to catch overwatch for the more important units. Healing and catch fire. And to surround stronger units, blocks their pathes and burst nasty stuff with an hail of grenades. And this job my Guardsmen can do more cheaply.
6. Are Ogryns worth it?
The two games I got them I was honestly not to impressed. But I have the feeling they have their niches against Tau and their stealth bullshitery.

So I have the feeling I can beat the AI with further playing and testing things out, but I just wanted to ask the community, maybe I do some fundamental mistakes. So I appreciate every tip and answer.
In this sense, the emperor protects, have a great day!

[KDubya]

I find Ogryns to be pretty useless, even with their extra shield tech they can put down with ridiculous ease by late game units. Plus they have poor armor penetration so they are poor killers.

For Edicts I'm of the opinion that they don't make much of a difference until your cities have 6+ basic production buildings. I skip them until late game when I backfill skipped techs.

[dexgattaca]

Hey, try beating it with the SM first to get a benchmark.
https://steamcommunity.com/app/489630/discussions/0/1742266965429663276/

Every army has The Unit that will carry you through the game. For the guard it's the Leman Russ Battle Tank get it ASAP and don't stop producing. Support with heavy weapon teams, guard units and Basilisks. Don't rush Tank Commander. I generally do a 3 city build. On smaller maps you may need to buffer with heavy weapon team spam to survive the early rush. Cheers.