A very fast-moving torpedo could afford to be unguided (or, more exactly, not to use its existing guidance systems much) in most of the Trek engagements. At long ranges, minimal course corrections would compensate for the maneuvering of the enemy; at short ranges, the enemy would not have time to dodge.
unless pulse phasers simply can't be aimed and they're significantly more powerful to the degree that would justify their use over the ENT-D 'ring of fire'...
They don't appear to be particularly powerful in conventional battle, but they do seem to be effective against the Jem'Hadar where standard phasers are not (at least initially). Possiby because they may have been designed to defeat the Borg by constantly varying their characteristics (so that each pulse is different) and this is how one finds the weak spots in Dominion shields, too.
Whether they can be steered or not... We do see them firing off-boresight in "Paradise Lost", namely about 50-60 degrees down from boresight, when Worf strafes the
Lakota by flying along her upper surface. Perhaps they do require some sort of a barrel that's difficult to mechanically steer (much like the Jem'Hadar bow cannon seem to have mechanical steering, as per "The Ship", and thus tend to miss at times where Starfleet strips always find their target).
OTOH, it would have been much cooler to see Worf fly across the
Lakota in a nose-down attitude, perhaps flipping end-over-end, to bring his (in this interpretation) absolutely boresight-limited guns to bear...
Timo Saloniemi