was looking for something to play and happened across this thread.
have played xcom since release and love it, still play it now and then after a couple years gone by.
have beaten it on impossible difficulty (but not ironman).
for harder difficulties:
2 snipers, squad sight
2 support (medic, fast run)
2 support (cover fire)
not created equally (random stats: restart till you have 3+ with reasonable accuracy(60+))
finish the first mission with your 3 surviving, or restart.
then play as normal, spend lots on recruiting, and sack everyone with crap stats, and only use non sniper/support if everyone is in hospital
only need to tech weapons for sniper and rifle(a little pistol for early game till snips have squad sight)
use grenades at start, loss of income is better than dead.
use cover, always.
all support carries med packs, use them
everyone carries a scope, accuracy is paramount.
designated runner = suicide scout, carry a vest/armour upgrade. single move forward, others shoot/cover, then runner moves back.
creep forward slowly, take your time
use cover, always!!
the expansion is really cool, too.
think i'll go play it again now