oh god i knew there was a reason I liked Mamanbou. this thing has been growing steadily on me ever since i saw it; I don't care about Faildisk so it didn't matter to me that it doesn't evolve into Mamanbou. Actually, I prefer that it doesn't, since I strongly dislike (very strongly, in fact) Luvdisc. XD
First of all, understand that while 165 / 80 Def / 45 spDef might seem stupid, it actually works out just fine. When you give Mamanbou a careful nature, and you have the EV spread I have, this sunshine girl will have 526 / 206 / 206 (at level 100, with 31 IVs in each of these stats, which mine will deffo have) in each defensive stat respectively, which is actually quite bulky when you consider the thing only has 2 weak, so unless it's a SE move or something atrociously powerful like Chandelar's Shadow Ball, sunfishy will be fine (it learns Light Screen).
Second of all, understand that Mamanbou isn't designed for offense; 75 attack and 40 spA is, simply put, idiotic. However, it doesn't matter, because the thing was supposed to be supportive anyway. It can Light Screen for its teammates, it can use Safeguard to prevent status, it can use Heal Beam on its mates in a double or triple battle (thus healing half their health), it can use Wide Guard to protect its mates from moves that would otherwise hit them all (and in doing so, allows them to set up) and it can even use Rest in sync with Rain Dance activated Hydration.
But of course, the award-winning thing about this fish is that it can use Regeneration in tandem with Wish. No other Pokemon can do that, except Tabunne, and her typing is worse than Mamanbou's, not to mention she hasn't got 165 hit points under her belt. Plus I hate her (she looks so stupid, seriously) so she doesn't count; plz 2 be usin' Clefable or Blissey instead, thanks. Ofc, Mamanbou will not see much use outside UU, but still, it's a pretty damn good pogey in my book.
So yes, I love this thing. It's a perfect support Pokemon; who in your team (whatever it happens to be!) wouldn't welcome a Light Screen + Wish Ofc, if you have an excess of Grass + Electric weak you should probably not use her, but my team has no fear of Grass or Electric moves at all, so they cover both Mamanbou and Cloyster perfectly (Roserade packs a double resistance to Grass, Mebukijika is actually immune to it, Jaroda resists both, and Torterra is immune to electricity). So for me, Mamanbou is a winning addition to my team.
Also, ocean sunfish irl are win. :D They feed on jellyfish (that's why Mamanbou is next to the Water/Ghosts, hurr durr).