When rendering additional passes together with a beautypass and having passes like world coordinates, normals, UVs and alike be sure to exclude them from the AA (“Consider for Antialiasing OFF”) otherwise you will most likely render at MAX AA for every single pixel.

Why you ask ? because the sampler decides based upon brightness and contrast (amongst other things) if a pixel needs more samples or not. Worldspace positions are easily 5000 or even way more…that looks as if it was VERY bright to the sampler and hence he oversamples as much as you let him. Result ? You could also render Fixed Rate with SubDivs as your former Maximum setting