Not bugged.

Playing Expert:

The Experimental Eye of Darkness regenerates so fast that unless you have a large number of heavy bombers attacking simultaneously it will destroy enough of your bombers that the remainder will not do enough damage to kill it.

I went with 8 heavy aircraft buildings pumping out continuously at the 20min mark and had 30+ bombers by the time the Eye of Darkness got to the choke point north of your base, at the 30min mark. They destroyed the Eye before it could get to my base.

I was trying 6 heavy aircraft buildings and only getting out 20 odd bombers by the time the Eye arrived. The Eye destroyed them enough that the remainder could not do enough damage before they also died.

I might try the narrative suggestion of multiple Leonidos Juggernaughts but I suspect that it will be extremely difficult to get enough out by the time the Eye arrives at the 30min mark.

The Eye of Darkness one shot killed my Juggernaught without breaking stride the one time I tried that so I hate to think how many Juggernaughts I would need to kill the Eye of Darkness.

Top of 2nd Post. I am playing Expert. It is very insane.

One observation though; sometimes the enemy comes at you extremely hard with multiple points of attack and several dreadnaughts.

This makes it difficult to judge the amount of army to build to combat this. You need to stop building army for defense at the 18-20min mark and switch to just building bombers only. I add several fighters as extra defense here as well. The strategy calls for careful control of nodes and production and keeping them defended at all costs. I take half the map. LOTS of refineries.  

The AI is not very consistent in this scenario as sometimes it hits you hard with air and not so many dreads. Air is easier to combat in this scenario.

30+ heavy bombers wacking on the Experimental Eye is fun to watch. They do die but I have them upgraded to level 4-5 on both damage and armor, so they can take a bit and dish out some serious hits to the Eye. 

Lots of fun. I was just going to "hang up my boots", stop playing this game for a bit as I had been through all the previous scenarios several times trying different strats and was getting stale.

Then behold! Out comes Secret missions and I am a happy camper again. Enjoying the new scenarios tremendously guys/devs/gals? Fantastic job and very nice way to keep the game regenerating. Cheap too at 4 bucks and I will happily keep paying for any more soooo..

Many thanks people