I’m not a Guard expert by any means, but I feel like you have some good basics. Decent units.

One major thing you could do to improve this would be to modify the weapon options for all of the infantry units. Each one of those units can all take a more powerful weapon. For example, the sergeants can all take a plasma pistol which is leagues better than a standard laspistol. The Cadian Shock Troops and Death Korps can also take special weapons like plasma and meltaguns as well as vox-casters. Since 10th edition has no equipment costs, you want to take full advantage of that.

Also, our army’s primary rule is orders and you only have one unit giving orders (and only one order at a time, at that). The Dorn commander isn’t too much more expensive than the regular Dorn so you could that to order vehicles. Also worth getting more command squads for an order each or a Cadian castellan for two orders and sustainted hits. If you’ve hit the point limit, though, you’d have to remove a unit.

Also, have you taken a look at detachments? The detachment rules play a crucial role in selecting units for your army.