I'll take mortars over turrets anyday. The enemy will wipe out a turret before it can fire a second time, where-as I can hide the mortars around a corner and pummel the enemy for a while before they figure out where I am.
Before walking up to a doorway, set up the mortar against the wall closest to the room. Set mines in doorway, turret just back from doorway, then set up your crew back by the mortar and slaughter any that come out of the room.
Occassionally walk into the room, fire once, then retreat to keep the baddies coming out to their slaughter.
Fleet Admiral T'Kehl - M.A.C.O. Vanguard Force (Sci Odyssey - USS Archimedes)
Fleet Admiral Shivers - M.A.C.O. Vanguard Force (Tac Escort - USS Abraham Lincoln)
The Federation's most successful counter to the Borg and Iconian threats.