Did you try playing with orbitals off? Or the middle option, which allows some orbitals but turns off some of them. It might have given you a more enjoyable experience.

I think they could improve how the higher ai levels get quanta because orbitals can happen too often while they get their big boosts. Perhaps let them keep their eco boosts but cut down their quanta boost a lot so they can't spam abilities so much, especially when vs multiple AI. Or make it a player tweakable option. AI needs a lot of work overall tbh. 

I don't agree with you on MP.  In ranked you are unlikely to get large armies it is true but if you find the right people you can have decently large games. Plays out completely differently to vs AI.

"The reason why the game seems dull is the AI behaviour and general gameplay inconsistency."

IMO, the inconsistencies are what keep me messing around with the game.  

As to the orbital problems, I was going to suggest that there are unit nullifiers available as well. In hindsight, their range was nerfed a bit too much considering the army formation tweaks that happened later.  Yeah, it is frustrating watching multiple Detonates/carving lasers insta-wipe the expensive vanguard of your army.

I have to agree here, Quanta is broken in the higher level AIs.  Since they already have an eco boost, I say let them build the generators themselves.

AI really does need work, especially PHC. Is there even a faction difference in the code?

This is actually MORE options to tailor a game to a players taste.  It seems in your case that this is not really viable for your troubles. All of that Quanta would simply be poured into unit/structure upgrades that will ROFLstomp your seemingly powerful units in a similarly frustrating manner. Ever seen a smarty/barrager w/25k hp?  

I would encourage you to at least check back peroidically. This game is still a work in progress and that is keeping my interest so far, despite it's shortcommings.

At the moment orbital nullifiers are not well distributed among units, they just stand in the rear of the army waiting to be focused down by AI. I suppose they can make orbital strikes like end-game powers hence limiting their power and availability.

I don't find the game so hard, but I think that these issues are not just "personal" and more than a nuissance.

Well I don't find AI that hard, I'm able to win on Tough and beyond (only in smaller maps though) even with these ingame flaws. Actually I think that there's an asimmetry between the number of actions required to use orbitals and the number of actions required to prevent them. Calling a strike is a matter of few clicks, while countering it requires a more intensive micromanagement (keeping nullifiers far from harm's way, put them in build order, counter orbitals etc.). That means that this is not a issue related to game difficulty, making the game more frustrating and less rewarding for everyone.

SC2 handles this perfectly.  The game says "Nuclear Launch detected" and shows a red circle with a countdown, giving you time to react.  Something like this would help in this game with the detonates.

Well, you do have a cost association with the most damaging orbital, but that doesn't stop you from spamming all the others. When used effectively the smaller orbitals can have a devastating effect on your enemy.