I was still regularly fighting Gillmen crews all the way up to August. Tasoth were more frequent in smaller USOs at the time, but I had previously only faced them on an Artefact Mission and a Tanker Ship Terror. My other Cruise Ship Terror (there were only two, on months 4 and 5 IIRC) was a Mixed crew.
OK, I was doing some more research on TFTD settings, mostly in wiki and the code. I was really surprised by several things that make probably the game much easier, if played quickly (the way you did). Also it makes the game very boring (tedious).
--- First and foremost: half of the alien bunch are crippled. We all remember Lobstermen, Tentaculats and Tasoths, right? They gave us the creeps. But the rest? I always thought TFTD had decreased number of aliens, which seems to be wrong. Where are they?
Bio-drone... is horrifying until you know you can drill it from vicinity. It will then try to attack with melee, which is bugged = 0 damage. Still, a threat.
Hallucinoid... has ranged attack similar to Sectopod (!) from X-com EU so it's frightening to behold one... wait! Its ranged attack does not work (bug). Next.
Deep one... cannot spit beyond 7 squares. (So they did not learn from Celatid??) Next.
Xarquid... rarish. And very poor as well, since it has few shots / turn and it makes a big target. Easy kill.
Triscene... is less frequent than tornadoes in my country. Probably bugged. Has comical weapons he never uses.
Calcinite... the movement of every melee alien in the game is bugged. They are shy. This guy does not look like frightening alien and indeed he is not one.
Gillman... Isn't he worse than his flying counterpart from EU? He's just same useless guy minus flying. Should not TFTD be harder than EU? If you played most of your mission against this crop and avoided bases, it
probably was easy.
--- Second: The mixed crews I was referring to can be found very early (yes, even month 2) on the Cruiser ship missions. These are irregular Terror-site, so they have special set-up. You were lucky to get them on 5th month, methinks. Still, only 7 casualties is incredible, if you did it without reloading. I find mixed-crew Cruiser + ironman unwinnable even with top weapons. Two stages are just too much.
--- Third and last point: TFTD really becomes boring quickly, quicklier than EU for me. The alien variety is missing (75% races are poor or very rare), and the terrain variety is broken. TFTD has so much better terrain and maps than EU. Sadly, 50% of the time you get two most frequent terrains... so for all the cool bunch of TFTD terrains, you have to fight through coral and sea-bed. Grrrr.