The underdog XP bonus makes effective farming irrelevant because as soon as you hit 2-3 levels behind, bam, catch up. It's a pretty stupid device to make shit teams feel like they aren't shit.
And yeah, the MMR is still fucked, you will get rank 1's grouped with rank 50's. If you're the rank 50, maybe you're the drag tbh. Myself I 've only got to rank 40 or something, I stopped bothering as there was no XP and I prefer working on master skins.