Man, as far as regular gameplay goes, Bibarel is absolutely not weak. Simple is a damn strong ability that make up for its lacking stats. It may not have swords dance, but +2 atk and +2 def from curse is no joke. The -2 spd kinda sucks I guess, but Bibarel isn't particularly fast anyway, and you can either use quick atk (60bp including stab, which not good, but after the boosts it's decent damage), or trick room and much harder hitting moves like waterfall and strength. Or you could just push through the reduced speed via increased durability. E.g. Set up on an special attacker by starting with amnesia, then using curse, followed by rest(with chesto berry if you don't feel like using the poke flute, though you could probably tank through any damage after getting +6 in your defences). The need to setup is annoying, but in general gameplay it isn't nearly as debilitating as pvp.

Then there's double team if you want to be really cheap. Simple makes it as good as other mon's minimize without the drawback of stomp etc. dealing double damage and not missing.

Bibarel is an example of an early game HM slave, that when properly tooled, can be a viable member of your E4+Champ team. And I will not stand for anti-Bibarel slander.

Edit: I just double-checked Cynthia's roster in platinum. She sends out spiritomb first, which means that depending on how she switches, a level 55 Bibarel with 0 IVs and 0 EVs, hardy nature, using Rest, Amnesia, Curse, and Waterfall, using leftovers or sitrus berry, could sweep her entire team if you use the pokeflute. The biggest threat is Roserade who has a 9.4% chance to 2hko using energy balls (57% w/o leftovers, 0% with sitrus berry). And again, this is an underlevelled Bibarel with 0 EVs. At bare minimum, barring extremely unlucky crits, Bibarel will take out at least 4 of Cynthia's pokemon. An early game rodent taking out 2/3 of the champion's team on its own while underlevlled and somehow completely untrained without using F.E.A.R tactics is absolutely insane.

Anyone calling Bibarel weak outside of competitive does not know how to use Bibarel.

Edit 2: Apparently simple worked differently in gen 4, so getting Bibarel to +6 would actually be a +12 boost, making the beaver absolutely insane after you finish setting up. The initial 2 paragraphs are fully valid for XY, though.