The rapid-fire ability plus 'ammo magazine' of the Omega torpedo is useful for spike damage when shield facings are down (5 torp hits in quick succession), plus it makes a nice torp spread, but it doesn't work with torpedo doffs and the magazine system limits its usefulness as an autofiring steady-stream weapon.
The Romulan torpedo is really slow and destructable even in regular fire (let alone high yield), and so not so hot against fast-moving low-to-mid-hp targets. However against big targets (and with a couple of doffs), by the time the torpedoes DO hit, the shields will be long gone and you'll have a big long stream of torpedo impacts from multiple doff procs spiking for big hit chains and ugly ugly plasma fires. Just be careful when using it at close range or you'll set yourself on fire as well.
Does the rapid fire of the Omega torp make a useful rear weapon? Spike all the damage as you pass (then it recharges while you face forward) or is it still rather poor (eg. worse than a turret or mine at the back)?