If we are talking better armed, the problem with that (being the TIE Defender) was that it was mass produced, just not to the extent Thrawn might've been hoping for. The outcomes of the battles and heroes participating may not be canon in the 2015 Battlefront but the TIE Defenders are present on the maps. Following the battle of Yavin, the Defenders are also able to be requisitioned by the 68th Stormtrooper corp on Tattooine (Star Wars: Commander), and due to a wreckage on Jakku at least one participated in the battle.

So even still the Defender didn't make that much of an impact because it was still in usage sometimes even on planets from the films (though not at things like Echo Base).