At least in the early- to mid-game, the setting of choice is, in a six-man team:
- three "Rambos" with a MG
- two Riflemen (as soon as I research the laser rifle), each with a Flamethrower in a backpack,
- one Grenade Launcher guy, with a Tokarev or Laser Pistol in the holster
Each soldier has a Medikit, of course.
The purpose is to eliminate most of the Scout or Fighter teams (3 to 5 aliens) in the first round. In the small maps, the GL soldier usually gets two aliens, each with a 15-TU three round burst. Then, the MG and Laser Rifle guys get the more distant ones. Generally, I found that a crouching MG-man is able to kill with a Full-auto shot even quite strong aliens at short to medium range (up to some 20 squares), because cca six hits with MG ammo kill any Taman and even a weakly-armored Ortnok. On longer ranges, a kneeling MG soldier usually gets at least two hits from the 20 Full-auto shots, even if the hit percentage shown is quite low (5-10%); this is just enough to kill a weak Taman, stronger Tamans or Ortnoks survive; but their Plasma guns are not sufficiently precise, therefore with some Medikit aid, a crouching MG soldier is usually able to win the shoot-out anyway, even without hiding. Laser rifles are nicely precise, so the two Pulse fires and one Wave is usually enough to get a kill or at least a "Mad Rage" situation.
In Harvester missions, the MG guys usually take a crouching positions with reaction fire at a safe distance (at least 15 squares) from the craft entrance; moving a soldier close and then running back behind the wing of the craft makes the aliens usually to go outside, where the MGs get them. Then, the assault guys drop their Laser Rifles, take their Flamethrower and go fry the last one or two aliens, who usually wait in the small central room of the craft, with stairs.
Especially funny are the Big City maps, where I just get the soldiers of the dropship, make them crouch in a straight line, and wait with Reaction fire on. As soon the aliens start to pop up on the top of that parking lot building, or what it is, they receive a welcome from the three MGs and the two lasers, firstly by Reaction fire and then by Full Auto and Pulse fires. Shooting upside is highly imprecise, but they die anyway; possible wounds on my side are promptly cured by the Grenadier in the role of a Medic, because the GL cannot shoot up to the top level of the building.
I do not use the Sniper rifle, because paradoxically, it´s Aimed shot is less precise than the Full Auto MG shot (of course most of the twenty bullets miss, but at least a few always hit, and that counts). All Plasma weapons and Assault/Bolter rifles are not useful due to low precision - they just cannot guarantee the result within one turn, where Laser rifles and MGs can (and Flamers/GLs too, of course). Even in close-combat role, the 14-TU, 5-bullet shot from the MG is usually quite OK, so my MG guys do not use pistols. Shotguns have neither sufficient range nor performance - at close range, GL or Flamethrower easily outperforms them in terms of damage.
Perhaps the MG/Laser combination will lose its power later, against stronger alien armours, and will need to be replaced, but the whole Plasma arsenal I invented so far seems inferior to these simpler weapons.
I play on Insane difficulty.