And to some extent that's why the Emperor is more expensive, and the Retribution is still considered underpowered for its cost. Obviously you have to consider the role. But in pure firepower terms, they're pretty even. For someone to be calling the defiant undergunned, when it's both clearly overmatched by every other variant and has the most tenuous role, it's a bit mind boggling.
I also absolutely hate the idea that a Defiant is going to be forced to be part of a squadron with another carrier just to make it worth reloading. One of the reasons for having one is because you don't HAVE another carrier. Giving it torps is such an obvious fix for this. The 45' isn't such a loss for these ships - they can still turn and fire their broadsides entirely forward or backward. It's vital on the Dauntless, because if it's facing the wrong way it's as good as useless, but the Voss have no such weakness.
Sure, against a single escort-type pirate a Dauntless is going to be better at chasing it down and destroying it, but if:
There are multiple pirate ships
And/or you've found a position the pirates have to defend (such as their base)
And/or they've got AC
And/or you're engaging in a skirmish with escorts from another power
And/or you have to defend a fixed position (such as a planet from invasion)
Then the Voss is far and away a better choice, and these are all vital roles that must be performed. The dauntless is good at one thing and one thing only - hunting down and destroying a lone, fast enemy vessel. The Voss are so much more than that.