Alakazam Raid
If one needed a sixth attacker, would double dark S/C Arcanine be worth using?
Answers
Use Gengar first, as it is your glass cannon.
This way he is less likely to face a spam of charge attacks until Alakazams filled his charge bar, and should be able to get off considerable damage before tapping out.
If he comes in later he is susceptible to getting KO'd before he has had a chance to make the most of his dps.
TL/DR Glass cannons first always, so they have more time facing less charge moves.
At the end of the day you either need a Mewtwo with shadow ball or a couple beefy Ttars, or a bunch of Shadow Claw gengars to do Alakazam. So most people go with beefy Ttars. And if you go the TTar rout, you seldom need 6 attackers.
PC/FB and PC/FS you might be able to get away with less but you certainly will fail against the other movesets.