Not to be destructive. But Oblivion's design is...eh. in first fight your just fighting a beefed up Pink-irised Retinazer-Spazmatism Hybrid and the second form is the same model as Spaz. In the Reborn fight your fighting two two-armed Skeleprimes on roids with different colored eyes but the yellow-eyed one has a different head model. both of their hands still have bone texture (I might be wrong cuz i couldn't see their color properly in the lighting) you may have different attack patterns with the lasers and the two black-irised first forms spazmatisms but Oblivion can really use a redesign with they're own unique designs without the recolored Base-bosses (The Twins) or little modifications to the sprites (Yellow-eyed Skeletron head). Not trying to nitpick i'm just suggesting that you can improve and I hope you can in the future.
P.S This was based by videos of Oblivion boss fights created in 2013-2014 that i watched. if the boss is already changed, don't mind this comment and sorry that i wrote this cause i didn't know this until now. Good day!