To be honest, I’ve encountered a Vex before. Hitting Phantoms are much harder because they live at a higher altitude.

MobB tends to start its attack run fairly far away and follows a relatively clear pattern making them easy to shoot. (Hitting one in melee when it dives is a bit trickier as there is a small window when it is in range of the player's weapon, but has not yet attacked.)

Vexes just seem to be jittery….