Classes: 2/3 are practically worthless before you multi-class them, character classes in this game are not very unique, most skills aren't that useful, and the only major difference is the type of equipment they can wear. The heavy is by far the worst class. They have trash mobility, their weapons suck, and it costs a lot of action points to use. This means they're generally out of range and are almost never able to make a shot. The only way to make a heavy weapon work is to cross-class them with sniper and equip them with sniper gear, but I classed them into assault and just had them bash aliens to death with their weapon. Sniper rifles shouldn't be that bad, because despite the fact that snipers also have trash mobility, they can hit from a farther range, but it's also very difficult for them to get line of sight. A lot of enemies in this game start inside buildings or behind structures. Assaults are a good all rounder class and have by far the best mobility. This is the class I relied on to carry me, as my entire strategy was to get as up close to the enemies as possible and kill them all before they could react, which brings me to the only skill in the game I would consider useful, dash. Dash lets you move at half your full range of movement for the cost of WP instead of AP, and you can spam it for as long as you have WP, which was usually 2 or 3 times a turn in my case. You use it to get close to the enemies, and then you use your AP to kill them all, which will get you your WP back for next turn, so you can repeat the process. There are other classes you can recruit from the other factions, but this was by far the best strategy I could find for what was avail be to me.
Oh and I don't really want to write a paragraph for this, but the technological research is lame and there's no real upgrade path for equipment. From what I could tell everything in this game is meant to be a 'side-grade', as in nothing is supposed to significantly outclass anything else, or that some equipment is meant to be stronger situationally, but what this actually means is that most weapons are useless.
Probably nobody is going to read this, but I had to get these thoughts out anyway heh.