MNK is still the highest single target DPS. Final Coil bosses have hardly any downtime unlike previous coils so you won't lose GL3 if you are good. There's maybe 1 occasion each in 12 (transition to adds phase) and 13 (Teraflare) but you'll have PB back up for both those times.

NIN is only maybe 10-15 dps behind though, and the utility they bring to the raid more than makes up for it.