I'm going to feel bad about abandoning my survivors. My Leader is 13th level and a skilled sniper/medic. My remaining crew is an Engineer (worthless), a Soldier (worthless), 2 Recon (awesome), 2 Scavengers (awesome), and 1 Medic (useful). If I had to start over, I'd have 3 Recon, 3 Scavengers, and 1 Medic by now. That would give me two good 3-man raiding parties and one 2-man for quick controlled jaunts. I expect Engineers will find some use when it comes time to enable Crafting (or not, it wouldn't surprise me).
The types of weapons each class is specialized with:
Leader - None (I generally use a Sniper Rifle)
Soldier - Assault Rifles, Melee, assume LMG's (haven't found one)
Engineer - Any Improvised (Rifle, Pistol, Melee, SMG)
Recon - Assault Rifles, Improvised Rifles, Sniper Rifles
Scavenger - Shotguns, Pistols
Medic - SMGs, Pistols
Levels that I've found types of weapons:
Sniper Rifle - 7, 13, 14 (rare weapon type; only have 1 level 7, 1 level 13, and 1 level 14)
Improvised Rifle - 9
Assault Rifle - 6 - 8
SMG - 8-14
Improvised SMG - 2-5
Shotguns - 5, 8-14
Pistol - All
Improvised Pistol - 4-6
Melee - All
Improvised Melee - 7-14
The Engineer starts of with ranged options and degrades into melee only specialty weapons. The Soldier gets Assault Rifles (which are still good against level 14 enemies) around level 6, but also degrades into only melee options. The Recon gets a good selection of Assault and Sniping. The Scavenger's shotguns never go out of style (the level 12 Tactical shotgun is awesome). Medics ... well, they heal people so it's okay that SMG's are pretty weak in general (I don't think the DPS number accounts for 25-50% accuracy)
I've hit a point where I'm basically running maintenance and slowly crawling towards the next survivor upgrade. Getting the 9th one is a huge challenge because I've built every building I can and all that's left is to upgrade them - each upgrade only provides +1 security or +1 comfort (some provide +2 but are hugely expensive).
I think I needed 65 comfort and 75 security to get the 8th survivor. Getting that meant building everything, including 3 guard towers. To get the 9th I need 85 comfort and 130 security. It's a crazy huge step, especially when I have to get it one point at a time. Granted, there are several "Security" structures that aren't in the game yet, so maybe I'd be working on those to get that 130 number.
The actual missions, while repetitive, offer a lot of good old fashioned isometric zombie slaughter. Still fun, and really the only reason I keep coming back.