Remember that there is completely different set of PvP weapons in retail, which is evidence that issues from the progression of the single player was to side-stepped in competetive play.
Except this set of weapons is also hilariously unbalanced. Look up the stats for the Mekhu HL7-D, it's the best MP weapon by far. Not to mention that not all multiplayer modes use "Dogfight" weapons. Then look at the UD-D Kayser and see how incredibly bad it is. The Kayser does lower damage than the Subach while costing literally 10 times more energy to sustain. The Subach HL7-D while not as stupidly overpowered as the Mekhu is still vastly superior to all other options, having the 2nd highest DPS and the lowest energy drain. Only the Mekhu's honestly idiotic damage beats it(it has better hull AND shield DPS than the singleplayer Kayser while costing the same energy as the singleplayer Mekhu).
The Myrmidon is most definitely not a jack of all trades. Nothing about it makes it more versatile than the Perseus. It has 3 secondary banks but they're small and the compatibility is bad so you can't get much versatility out of them. The 4-2 primary configuration might offer some versatility... if the compatibility wasn't so bad again. It can't mount the maxim so you don't have good utility options for the 2-bank. It isn't very durable so it can't act as an assault fighter. You might think it's somewhat tough because of its massive size and the "Average" armour but in reality it's only very slightly tougher than the Loki(it has 10 less shields but 40 more hull).
The Mrym isn't bad because other more specialised ships perform each role better, it's bad because its stats are terrible across the board. The Perseus is better for every type of mission. Unless you want to claim the Helios compatibility is intentional despite those never appearing together.
With the bombers, the low primary energy capacity, is a clear move to push the use of secondaries for the bomber role.
Except this doesn't matter because their high shields grant them high shield regen which then lets them tap shields for weapon energy with 0 ETS on weapons.
And the biggest problem with this "planned obsolescence" theory is that the vast majority of weapons suck even if they're introduced later. The Subach becomes obsolete after you get the prom S, this is planned obsolescence. The Mornginstar is always useless, so is the Circe, so it the Lamprey, so is the Prom R. They all come later in the campaign yet they're all far worse than your starter weapon, the Subach.
With secondary weapons this is mostly true as they're obviously better balanced to offer a progression of power. The major exception being the Tempest which does the most retarded damage and is the first missile you have access to.
Aside from that you go from the Rockeye to the Harpoon, an objective improvement then from the Harpoon to the Tornado, another improvement, and then to the Trebuchet which is the best homing missile in the game and comes in later in the campaign. This is what primary progression would look like if it was actually balanced for planned obsolescence. But instead you sit on the Subach until you get the Prom S, and then add in the maxim for anti-subsystem work. The only weapons that get "improved on" are the Maxim being an improved Akethon and the Prom S being a better overall weapon than the Subach.