Right now there are a few things which are quite out of balance in the top half of the tech tree.
1) Laser small arms. They are so much better than any other small arm option it renders all forms of gauss worthless. I get the cost is supposed to be using Rares and energy but rares are not rare and energy has no weight so it actually simplifies your logistics. Maybe make them cost machines?
Lasers rifles are imo a tech level too low and probably 1/3 too powerful. Gauss of all types also needs a firepower buff and likely a caliber increase.
Yes, laser rifles are way too good. They have three times the fire power of the automatic rifles AND also a 50% higher caliber. They can rip apart tanks quite well. The energy cost of using them is usually no too much of a problem, as infinite energy is available by spamming out lvl 1 solar plants. Since they are in the same tech level as gauss rifles (which only have 25% more firepower than automatic rifles, despite being 3 tech levels higher), there is basically never a reason to get them.
There is simply way too large a hole between automatic rifles and then laser/gauss rifles. I would suggest moving Gauss rifles up a tier to Advanced Engineering and also improving their fire power to 150 or so. At the same time the fire power of laser rifles should be lowered to 200 or so. They will still be way better at dealing with everything because of the caliber differences. Combat armor counts as 40mm, which means gauss rifles only have 50% fire power against other infantry, while laser rifles will have 75% fire power. Maybe laser rifles should cost machines.
Charged Gauss Rifles should also be bumped up in fire power and maybe caliber. Maybe have them use ammo and energy.
2) Gas powered small arms are beyond worthless, they need to be at least as good as high speed MG/carbines in firepower to be even worth considering.
Yeah, I have never even considered getting or using gas powered small arms.
3) Missiles and Rockets do too much damage to assets. The no.1 strategy right now is to get within 7 hexes of your opponents cities/logistical assets and just blow them up and the only counter seems to be shield generators which are wayyy down the tech tree.
Being on the receiving end of this in two games, I can only support this. A single battalion of missiles will reduce a level 4 city to uselessness within two turns and to rubble within four. In general city assets take way too much damage too quickly from artillery, rockets and missiles. This problem obviously is worst against missiles because of their huge range.
4) Liquid armor is supposed to hard counter lasers but it's too far down the tech tree and too expensive to be worth using.
In addition, liquid armor uses Hi-Tec, which are very hard to amass in quantity in any normal time frame. Moving it up a tier and costing machines instead would make this a way more viable technology.
5) Walker based OOB needs to exist. While great they are hard to use as only independent units.
I don't want to go into the topics of OOB too much (despite having made the effort to at least catalog all of them in a War Room post), but in short: Missing walker based OOBs go hand in hand with the general problem of too many different OOBs being acquired/discovered by luck. At least a visible, tiered, OOB tree is the minimum required, better would be something similar to the way unit model development works (specifically the entire tech development, model type discovery, model design interaction).