i find that guardians with rerolled 5+ cover saves are quite resilient, and the cheapest thing to do is to just take bright lances,
so get two of those squads and you have your "sponge" to take fire,
then your going to need something to thin out infantry fast, i would suggest staying away from rangers, there not troop killers, and i would not recommend reapers with so many units to kill, your best bet is either scorpians or spiders, depending on your style of attack, one of the ideas though is speed, so if you get pychers give them bikes so they can get up close fast,
on thing you can do with a falcon however is to get a blasphemers team together, they consist of 5 warlocks and a seer, the seer has fortune and a witchblade, the warlocks all have wytch blades and 4 have destructor, that will burn a hole in the unit number of the imps, and then they can charge the tanks with st9 attacks, (its the equivelent of about 15 lascannons). then fortune the squad so you can survive the next turn of rapid fire and do it all over again...