Phalanx II comes in handy in situations where you can't come /SCH though. To be honest with the ease of EXP gain these days I change my merits daily since I have nothing to spend merits on anyway. If I'm gonna cleave, I'll go 5/5 Phalanx. If I'm gonna burn some empyrean weapon NMs, I'll remove Phalanx 2 and put them in Dia III. etc..