The Manticore is certainly a competitor to the Enforcer, but I think the Enforcer still has a place as I think you're overrating the Manticore somewhat. Manticores can either be built for missiles or guns, but not both, and their ranged support isn't really proportional to their 33% DP hike.
A few enforcer strengths:
-Excellent point defense. Whether vulcans, flaks, or dual flaks (depending on wanted investment level), the 2 side turrets give 360 degree PD coverage with overlapping forward and rear arcs of the best PD weapons in the game. They make very nice escorts for capital ships/cruisers because of this.
-Toughness. I think this is my biggest disagreement with you: the only things I've ever seen rush down and 'pop' an Enforcer are (some, not all) Radiants and full Tesseracts. They can certainly get destroyed, but last much longer than other destroyers would, allowing other ships to help them, so I agree with you that they should be operating in groups. But the reason to use Enforcers rather than more offensively oriented ships like a Hammerhead is because the Hammerhead would die if it tried the same thing. In particular, I like giving Enforcers eliminate orders against capitals, which makes them burn in, then later giving the eliminate to the rest of the ships. The Enforcer takes the brunt of the capitals firepower (and hopefully launches some sabots and hits with a burst of heavy needler fire) but it can survive that, and when the other ships engage the capital is fluxed up and firing at a target so they can approach without getting shot. This same toughness also makes Enforcers excellent for station busting: they can tank the gun firepower of stations and hit back with torpedoes.
-Anti-fighter performance. The combo of the first 2, and having all its firepower in turrets, makes Enforcers quite good vs fighters. This doesn't really matter until it really matters.
-Missiles. Like you say, a Manticore with 2 Mediums outclasses 4 smalls. But Manticores are more DP expensive and if built for max missiles can't be built for max guns. Considered as part of the whole package, the 4 small missiles are a strength when comparing to the non-manticore destroyers (HH, Sunder, Medusa).
-Long ranged possible build (if wanted). 2HVD + a Heavy Mauler or 3x HVD actually deals more overall DPS at 1000 range than a Hammerhead would (HH has less than 50% uptime in its system), outranges anything but a Gauss that a Manticore can bring and is competitive even in the 900 range bracket, and is flux light to boot (if not efficient). I have not tried this in this build yet this version, but I think an Enforcer might be able to support 4x long range guns as well. That would mean giving up the 360 PD, but it could mount a forward flak I suppose? Sunders both outrange and outgun this combo, but Sunders are glass cannons so thats a good thing imo.
-Converted Hangar platform. They have high OP/DP, letting them cheaply (from a fleet perspective) bring fighter wings, and it impacts their performance less than other destroyers.
Enforcer "ok" bits
-Gun Firepower in the midrange. An enforcer can comfortably support something like 2 Heavy Mortars and a Heavy needler, or 2 heavy autocannons and a mortar, etc - some combo of guns costing around 600 flux. The former combo puts them just behind a 'brawling' standard hammerhead (250 kinetic DPS vs 333) before the system, which gives them in total ~60% of the gun firepower. It's an 'ok' amount of firepower, but a lot less than the gun focused HH. Being purely turrets sometimes helps (vs frigates and fighters) but also hurts (less gun HP, more recoil). They will lose a pure gun duel with a HH eventually (but they win if they use their missiles, so that really depends on overall battle flow).
Enforcer 'poor' attributes
-Speed. Outside of their burn drive they are the slowest of any destroyer and are outrun by a lot of cruisers, to the point where I think SO is actually a bad choice on them: with SO they can barely catch destroyers and will get shot to death by things outside their range. They make very poor hunters (but good escorts and line/anchor ships).
-Shield. At 1.0 and with mediocre flux stats, its poor. Its not horrendous like it was when it was 1.2, and its not a liability, but its notably poor and makes Enforcers vulnerable to high per shot energy damage.
