Buck may try to stomp on you and scare you with his high health pool and regen. Just remember that Buck has a pitiful damage output, start on him early. If you are at or below 700 health, use an escape to regenerate. A clever Buck is deadly.
When u hear the Kinetic Burst sound or see the animation, use your shield to tank the next hit.
For her dash use Commander's Grab, that has a bigger hitbox, in the direction she is looking.
And when she ults, use your ultimate to take her out.
This is a very general tip and can work in many other cases with Seris. When you hear Drogoz ult and know he will target you (or to be safe) quickly go into shadow travel. This makes you immune to his ult and will confuse the enemy. Be fast, though!
Maeve is probably the safest pick against Raum, cause its hard for him to hit you. He also has high damage-falloff, you don't, so you can use that to your advantage and keep your distance.
Burn monster cripples you and prevents the use of abilities and it cuts off your escape, and it stops your ult. You have more range than Tyra though, so it's best to just keep your distance from her.