Reapers:
excellent early game scouts and demolitions experts. can have high burst damage with banish, special ammo and sup. magazines. however in the late game they are not needed.
skirmishers:
they are mediocre through and through (support, firepower, burst damage). no place in the late game. high mobility
templars:
the weakest of the bunch, their damage falls off and while they are good with blademaster against the lost, sharpshooters are better. they always felt like a liability to me throughout the game. they are good at aoe damage, but xcom2 is more about few, but very tough and dangerous enemies so single target and control is king.
my ideal squad:
===mandatory===
1+2) psi ops:
important abilities: all
equipment: mimic beacon + blue screen rounds
==> best support class with stasis, domination and inspire
==> reliable psi damage
==> reliable mechanical unit killers
3) ranger:
important abilities: run and gun + rapid fire
equipment: talon rounds + wraith suit + sup. laser sight + sup. mobility pcs
==> insane burst damage, insane mobility, can kill anything
4) sharpshooter:
important abilities: lightning hands, quick draw, face off, fan fire.
equipment: venom rounds + sup. scope
==> long range damage, high burst medium range damage, kills all the lost (you need the reaper order, between the eyes though), good pseudo aoe with face off
=== optional ==
5) spark:
important abilities: adaptive aim, intimidate, repair, sacrifice
equipment: sup. mag + sup. scope
==> shreds armour, good burst damage, aoe heavy weapon, can protect the whole squad with sacrifice (intimidate panics ~50% of all organic enemies, has insane tanking capabilities )
6) specialist (this one is debatable):
important abilities: they are all mediocre at best, you just need a remote hacker on some missions
equipment: medkit + skulljack
==> ranged hacker, use aid protocol on spark with sacrifice ==> spark has 60 defence,5 armour and panics 50% of all organic enemies that shoot at your squad
how to remove cover: no need to, psi dmg is independent and the other classes either have 100+ aim or enough mobility to gain flanking shots
concealment/scouting: no need to, if you trigger one squad stasis 2 enemies and kill/dominate the remaining ones. if you trigger too many enemies: use sacrifice on your spark + aid protocol
weaknesses: burrowed chrysalids
i can't see any of the new prestige classes in this squad. you could replace the optional soldiers, but you will loose the sparks ability to save your whole squad if you triggered too many enemies and your psi soldiers are for some reason unable to control them.
what would chance this setup:
-more enemies: psi ops are to insanly good because pod sizes are small, 2 psi ops can remove 4 enemies in one turn (stasis + dominate). when was the last time you encountered a pod with 5+ enemies and the last few could not be dealt with 4 soldiers?
-some sort of traps that would force you to scout ahead (you can just use some ability points to spec the ranger into a scout as well)