I’ve encountered that Cover bug quite a few times, that someone mentioned a page or two back. It’s annoying as all hell when you just can’t flank them, but they can flank you.
As for snipers, the squaddie rank replacement snipers, are pretty terrible if you just try adding them in after the bigger HP aliens come out. They don’t start with that great of accuracy, and don’t crit that often, and only can shoot once. But Squad Sight/ Double Tap sniper is awesome, and two of them can take out everything. The pistol skill, along with some of the foundry upgrades and Plasma Pistols are also nice. Though even without the foundry upgrades, my best sniper would often get pistol kills.
Assault guys are nice, Run N Gun and Rapid Fire and that auto-overwatch on 4 tiles skill is awesome. At least one required, an entire squad of them can be fun. Though they do tend to get themselves in more trouble than any other class.
Heavies, are meh. Their accuracy blows, their range sucks, and I wish their rockets shot farther. HEAT is their saving grace late game, but my snipers can usually whack the robots from farther away, and Rapid Fire on assaults will work better on most things and are more mobile. Early game, they are the first class that can shoot twice, which is nice, but they also waste ammo like crazy and have to reload.
Supports are great, I like them because of Sprint. Sprint + Ghost Armor has them move so friggin’ far. Makes for great Arc throwers, or to get that medic to the right spot fast. The three use medkit is pretty much a required skill. Smoke is meh, even upgraded I still seem to get hit more than I like, but it’s better than nothing. They also have decent accuracy and make good use of Plasma rifles. The rest of their skills aren’t noteworthy, the overwatch stuff is interesting, but rarely useful.
So, the TLDR version:
2 x Snipers
1-2 x Assault
1 Heavy, and those times where I didn’t take one, I didn’t miss them much.
1-2 Support