Prankster only affects status moves, not Foul Play/Draco Meteor.
Correct, but Mirror Move is effected by priority. And Murkrow has enough base speed he can foul play pokemon like Metagross no problem.
In-fact, I killed a Meteor Mashing Metagross lead just now in pokemon online with this set up:
252 Def 252 HP 4 Spe bold @eviolite
Calm Mind
Roost
Psychic
Foul Play
Murkrow 3HKOs a Meteor Mashing Metagross with Foul Play, living with 14% HP remaining and can choose to stay in and roost on the revenge kill if the target is physical (just hope Metagross doesn't get that attack boost). The point of Foul Play is to be a mixed wall. You wall special attackers with CM, kill bulky physical attackers with foul play, and psychic when you're at +4 or more SpA (and know you can take a hit going last). Murkrow also can 4-5HKO physically-invested Zoroark with Foul Play (a pokemon you might think could just wall him). And on targets with low base defense and moderate attack (like the seldom seen Pikachu and Sharpedo) Murkrow can easily 2-3HKO them.
Murkrow is pretty frail as far as walls go, no matter how you run his move pool, but he does well against many common OU threats.
And yes, if you try to Mirror Move Salamence WHEN he's doing Draco Meteor it will fail (or you'll do whatever move he did last turn). The point is to Calm Mind or feather dance or thunder wave the Salamence, take the DM, then reflect it back at him next turn. It's a little gimmicky, but it works just about as well as running Psychic on Murkrow.