So, I just did my first battleship UFO. It was fucking crazy, even on normal. When I ran into enemies, they just wouldn't stop coming. I had to chew through a pack of mutons, a pack of muton elites, a pack of mutons + berserker, two groups of heavy floaters, and two groups of regular floaters all without ever having a moment to breathe. I'm still convinced that the lack of time to reload and resultant need to either rely on sidearms or ignore the enemies for a turn turned that against me. Oh, and then, once I finished up that mess, I had to fight a sectopod with my wounded, barely holding it together, squad.
I won the mission, but only barely. I lost a colonel assault, a major support, a lieutenant or captain heavy, and a corporal assault. The heavy was bleeding out, I revived him, and he immediately got blown away by a Muton. My colonel assault bled out because I had no medkit left. The part that REALLY stings is that my rookie assault and my support didn't have to die. There was one sectoid commander left with like 3 health, my assault was mind controlled and my support was bleeding out with one turn left (and, as I noted, no medkits left). I had a shot with my remaining heavy, though, and he probably could have done it... except I accidentally fucking targeted the mind controlled soldier! So instead of killing the sectoid commander and walking away with only two lost men, I lost two more, and would have lost a fifth if the sectoid hadn't blown his final shot.
That was seriously the most insane mission I have ever faced in XCOM. I now have just my colonel sniper and other colonel assault (who was in psi training for the UFO... in hindsight, that might be a good thing) for ranking soldiers. All but one other guy are squaddies. I might be completely fucked, although it's normal so I can probably pull it out.
Moral of the story: DO NOT fuck around with battleships. They can wipe the floor with you unless you run a razor-sharp operation. I shudder to think what one of these would be like on classic or impossible.