Escort is escort. All defiant did mostly just to blow things up, and fast. Which is what escorts already do. Starting from T3 PvE I could go max impulse and start shooting from 10km, target would usually always die at 6km, even if it's a cruiser or battleship target.
T2 might require some slowdown, but I've pretty much never had to turn around to shoot my target unless if I was rushing into them with evasive maneuvers or if it was a mission where they spawned right next to me.
The difference is, the defiant used speed and switched targets as it flew by (if they lived), while in STOI escorts slowdown somewhere (park) and just shoot...than complain about lack of suriviablity...hehehe