The aliens have a weapon from that tier as well, they just don't use it on their ships.
Anyway, I pretty much just lost my I/I (Ironman Insane) Xenonauts campaign, which is also my first Xenonauts game post AI update. I'm going to keep going, but the primary base suffered a TPK so this is looking bad. Mild spoilers if anyone cares. It happened the first time I met those aliens who looked like they were wearing space suits.
Some mistakes were made, but mostly I should have just fucking run. I was completely unprepared for these guys. The tactics I used against the previous aliens didn't work at all. I bunched up my guys too much, causing them all to get suppressed and panic. The aliens apparently have a longer sight range than me which resulted in the early death of an experienced laser machinegunner. I got lax and didn't bring enough smoke because Secillians are immune. After 3 casualties I switched objectives to UFO capture, which would have worked but there was an open space in front of the UFO that three aliens could shoot into. So I needed smoke, which means I needed to run back to the squad leader's corpse. Secillians and Ceasans had trained me to think that flank and rear guards are useless, this utterly bit me in the ass. While a private ran back to grab the smokes one of those crazy disk things circled around and caught the squad from behind. In the end the last man standing was a private who's riot shield broke. He pulled out the shotgun from his backpack, rushed out into the open, and one-shot an alien before being gunned down.
For the next run I'm going to move away from the whole 3 machinegunners to a squad thing, which I was mostly doing to be entertaining anyway. I have very much learned the value of TUs in I/I, as I frequently wanted a maneuvering element to flank suppressed enemies with and no one was good at that. I'm thinking of adjusting my strategic build but I'm not quite sure how. I think I'll focus more on the interceptor game to keep my funding up; ultimately the relative benefits of capturing versus bombing UFOs are too low for me to need to capture every UFO I down. So I'll probably get Foxtrots up and just blow up any corvettes I see, which I assume is what Foxtrots do (I didn't get them). Finally I'm likely going to rush stunning rather than lasers because lasers are expensive for the (admittedly quite good) benefits they provide. Stunning will allow any soldier to take out an alien should they get close, which is massively useful as in I/I half my Secillian kills were in close range with LMGs, because that's what it fucking takes.