So at this point, I have played the prologue, the imperial campaign, and the Necron campaign to completion on epic difficulty, and gone halfway through the imperial guard campaign again, still on epic. I thought I would write a few notes.
Firstly, the imperial starting fleets are just silly. Ignoring power, look at what your introductory experience is. You are asking the player to manage an Endeavour, a vanguard, a lunar, a firestorm, and a sword.
Why is this bad? Well, you are introducing any new player who is too intimidated to try multiplayer to the game by asking them to manage:
Two torpedo ships, one of which is short burn and one of which isn't, so the torpedoes don't move the same speed, and make sure that one of them has a loadout of so few torpedoes that a pair of frigates can shoot them down from 4.5k range without trying.
One squadron of strike craft and no other carrier power, so that it's assault boats get shot down by a frigate.
Six admiral abilities spread over 3 ships
And 2 escorts which don't have the same firing arcs.
Not to mention that you managed to put a 240 speed ship of the line in with a bunch of 160's.
And for some reason, Start the game with a manadatory commander who has a bonus to nova cannon cooldown but no nova cannons, that you cannot disband.
This is a terrible introduction to your game. You are giving people the impression that trying to manage a 600 point fleet well is incredibly difficult, and you are also giving people almost no early decisions about fleet composition.
Cut the number of fleets to start the campaign by at least one, and then add the third fleet to the game after you rescue it from those floating explodey thingies in the scripted mission on Cadia.
And don't start with a vanguard. That's just silly. The vanguard offers a critical mass of exactly nothing: it's not good enough at boarding to be good, it's not worth microing a single squadron of strike craft and that's just an exercise in frustration for a newer player. It's not a good supercharged void shield ship either, because there already is a linebreaker in the starting fleet: it's spire, with a ramming spur, the rammnig spurs specialization, fast burn torpedoes, and double the shield values, and not needing to waste his repair cooldown on honor the chapter. It's also a light cruiser, and you have now reworked vision so that light cruisers are completely useless at that, because you can't even see people at your detection range any more.
You don't want to saddle a player with poorly chosen commanders that you cannot disband, that tie up all your fleet maintenance with bad ships. Start the game with ships that actually work well in small fleets, which are easier to micro, and which don't tie up the entire pop cap of the fleet with a bunch of very inflexible stuff.
Oh yeah, and make planets that generate resources a lot more obvious on the map. That's a giant trap for a new player, who is likely to run around capturing penal colonies and Agriworlds, and not understand why his fleet is losing money. Forge worlds need to actually look distinct on the campaign map.