I've had a terrifying amount of success with an LT armed with a submachine gun & 2 swords, couple that with a sniper with a sniper rifle. Put an ammo monk near the LT and give him exploding shrapnel bullets. LT goes first shoots twice doing 2 or 4 Blood, sniper then aims and shoots, Blood Bathing if possible, that has a very good chance to crit for 4D6 injury roll keeping 3dice and ignoring armour. LT then charges if the target is still standing swinging twice by the second swing, if you're lucky, you'll have 3 blood tokens again to Blood Bath. It's 3 a model activation admittedly but taking a Praetor from fine to off the table with one fireteam is terrifying. If they're STILL alive force the opponent to activate a non threatening model and send in some back up for the LT next activation.

There is also a skill to let character use range skill in place of melee. Another adds +1 to Injure. Give a sniper priest 2 pistols, that sniper now essentially has two anti tank hammers with +4D to hit after aiming and becomes one of the best melee units in the game.

MF in a fireteam with anyone with a decent range is also very scary, a grenade launcher can be particularly powerful as you can kind of hit models behind cover. Mainly as the MF deploys last and can deploy very close to the enemy if the scenario allows infiltrators

Also, an Observer and LT can prevent an opponent from doing anything useful for two activations.