Medusa is objectively the best destroyer, both as flagship and as escort in larger fleet, as it has the advantage of ballistic mounts and armour of midline ships, but also the flux capacity and shields of a high-tech ship, and the mobility of its phase skimmer. It even has rear mounts wich will add you some PD without sacrificing frontal firepower.
About AM blaster on temptest, you should try ion pulser instead. IDK, why alpha damage is so popular, but if you install battle analytics mod, you'll see that the numbers for AM blaster are consistently 4-5 times lower, than PL or IP. And I don't think having two of them is a good idea, as it also against sustained firepower and is very bad against armor, though I never looked into that, never thought two pulsers are a thing.