For what it’s worth, over the last 10 years I have used 4 different hardware i/o products: AJA, Blackmagic, DPS, and BlueFish. From an engineering standpoint (though I’m a novice-level video engineer), the AJA hardware was the best at complying to what video output should be, based on looking at ‘scopes, colorbars, etc. (although DPS was pretty good too).
So I would keep your AJA hardware, and stay on top of driver updates for Premiere.
-Jeff