3 characters that can counter the miko tank combo

Oscar mike: Oscar mikes fire grenade and air strike can bruise up the tank or you can shoot for miko and keep him off the tank for a bit
Orendi: orendi can use shadowfire pillar and paradigm shift to annihilate miko or bust up the tank
Phoebe: phoebe can use phase distortion to get behind the tank, slow him and miko down and kill miko.

Foxtrot can Frag cannon and “wound” the tank quite easily. With good communication this would bring the tank down to the dispair of his miko.

Caldarius, blind cut miko healing beam and his constant bleeding and deadly accuracy with high mobility.

He can flank, bleed the tank and blind miko and follow landing every single crit. If miko flees the tank is alone.