A tips to know, if you want your companion have insta hit on all their powers, turn back when you order them to use a power. When you dont see them, they use instant hit and banshee cannot parry insta hit. In this case, idealy you must also use yourself instant hit powers, like reave, drain, sabotage, overload. These powers cannot be parryed.
by example, as engineer, you can order Tali to use drain and you detonate it with overload. but sabotage ensure you tech prime the target after 1.5s but drain does not. drain prime the target if the shield/barrier has not been fully removed by the hit. Also instead using yourself a tech detonator, you can order a companion (ida) to insta hit the target with incinerate if the shield is low after the first tech hit. In this case you receive a tech burst + priming for a fire explosion, all in insta hit.
By example, continue as engineer and insta hit, you take Reave as bonus power. As companion by example, you take Liara and ida.
1/ You prime with sabotage (insta hit) and wait 1,5s for tech prime 2/ You order ida to insta hit with incinerate (you receive a tech burst x% of sabotage + You prime for fire expl) 3 You order Liara to insta hit with warp, you get a fire explosion + priming for biotic 4 You insta hit with your reave as bonus power for a biotic explosion
You have done 3 combo, all in insta hit. Now you can send 1 or 2 reave to benefit from the debuff of warp if it is necessary. Else kill other mobs with others powers during the time your companions reload their powers.
another tips to know about banshee, they have no defense when they teleport, this is one of the best moment to kill them with insta hits.