I can't see any alternative. There isn't a common English verb form of these roots: influx - influence - (v.) to influence, but -ence is obviously a noun suffix converted to a verb. If we took verbs out of Latin -flu- we might expect "to influe" or "to efflue" or "to reflue", but I can't think of anything existing like that. So "efflux" is the natural English verb from nlun "efflux", isn;t it?