This was discussed at the top of the thread. The issue is that there's no reason for it. A closer look at the Paradigm reveals that it's dotted with large turrets and actually seems to be larger than other destroyers... plus the description that it's a particularly advanced warship from Origin FX... and the fact that even in terms of in-game weaponry it's more heavily armed than destroyers that came before it...
Puts us back where we were, doesn't it? I mean, without a size stat, we're pretty well stuck.
You know what, forget about size. Let's look at their respective capabilities for a moment.
Paradigm: 200 kps, "Poor" acceleration, "Poor" Maneuverability, ?? Shields, 80/65/65/50 cm Armor - 2MES, 2TAC, 1IPC, 3xLASTUR, 3xMASTUR, 10x1DF, 2x1 IR, 1x1 HS
Gilgamesh: 250 kps, "Poor" acceleration, 2 dps, Phase Shields, 250/200/200/250 cm Armor - 2FLAK, 2AMG
Southampton: 200 kps, 10 kps^2, 5dps, 2000 cm Shields, 1000/1000/1000/100 cm Armor - 9xLASTUR, Light Fighter compliment.
The thing to note is the type of armament and the relative strength of the defenses. While the Paradigm may have more guns, none of them would be particularly effective against enemy capital ships, but they would be good against pirates, raiders and such. I mean, the Antimatter Guns on the Gilgamesh can bypass shields, so that's a definite anti-ship capability. Southampton...well, it's guns aren't all that strong necessarily, but they'd be sufficient to swat down incoming torpedoes or give incoming enemy bombers hell, and that's where its strength of defenses comes into play.
Strength of defenses...well, a centimeter of Durasteel is a centimeter of Durasteel is a centimeter of Durasteel. I mean, you can conceivably kill a Paradigm with civilian-grade weapons, while its contemporaries generally require torpedoes.
The Paradigm is clearly not a front-line warship - no matter how "advanced" it ostensibly is - but as a pirate interdictor, it could do the job without taking one of those heavier craft off the lines. It'd probably be cheaper to build too...all the more reason to even build something like this in the first place.
Anyway, I guess that's my argument for calling it a destroyer escort. It is stronger than the Exeter and Venture, no argument there.
Without going too deep into size, I'll play devil's advocate by saying that the ship could be really small and the guns normal-size, thus appearing big relative to the ship. Like I said, though, without a size stat...