What happened to all my battling prowess?

Alright, I'm starting to get discouraged with Pokemon Battling.

I can breed and train like no other and all of my Pokemon are pretty much perfect in every way, and yet I continue to lose. I have lost my last 4 battles (3/4 horrible losses mind you) for no other reason then my sweepers are not doing damage as they should or they miss quite often despite high accuracy (I continue to miss with attacks at 90 accuracy 5/6 times I use them). They miss when its important for them to hit the target and get KOed in return too.

My only pokemon that seems to even be doing its job right is my Forretress. It spikes, toxic spikes, stealth rocks, or rapid spins, then is destined to die to make way for a sweeper who should now have a decent time sweeping!
Should mind you, yet even with Toxic Spikes making a dent on defence and stealth rock ruining chances of Focus Sashers my Sweepers (who have max speed and attack depending) still cant get the KO they should normally be! They just get my opponent close to a KO (maybe take out a few really low defenced pokemon) then FAIL in their job to get more KOs.

My Stallers are even disappointing me despite their top defences. Somehow people can 2HKO my stallers who used to take 3 hits to die. Its agaisnt the same type of pokemon I've been fighting before I took a break, and now that I'm back I cant win a damn thing.

Did something happen while I was gone? Do all of my oponents sweepers now carry 200+ defences on a daily basis? Has accuracy been changed? Or have I just simply lost my touch in battling even though I'm pretty much sticking to my old plans of softening up my opponent with Stealth Rock and perhaps some spikes before bringing out the big guns? I dont get it. I stopped battling for little under a month, Garchomp got Uber status, the entire Tier list got f'ed up on Smogon (thus everywhere people are using it depite so many arguments), and suddently my team is nowhere near up to par with people I used to wipe the floor with!

This is seriously disturbing to me how my 90% accuracy attacks will miss, yet my opponent using attacks that have much less accuracy (70%) can hit with ease. Plus my best Walls being KOed far to early, my sweepers not doing as much damage as they used to, and all this in only a few weeks.
What happened? Seriously! It seems now all I can defeat are people who dont EV train or are new to the metagame since everyone else has defensive sweepers and walls that pack too much of a punch.

I dont even know what to do anymore about it. I've checked my pokemon's stats and IVs again only to see the perfection I bred, yet they are not nearly as good in battle as that would normally be. The battle tower is still a laugh to me (even though I can only get to rooms in the 40s before being eaten alive by a team seemingly built to destroy mine) and its only WiFi battles I've been suffering through. Its laughable to get this worked up over a game, but for all the time I spent breeding and training only to get destroyed online when I used to be the destroyer is pretty brain racking.

I dont know...
Maybe I should just quit battling altogether, but then I should just drop my DS and forget about Pokemon if I'm going to give up like that. I dont want to stop battling since it used to be so much fun, but now its more of an embarassment to my name as a trainer.
Maybe its because I've been altering my normal party and strategy too much? Normally I like to set up some spikes and rocks before stalling and making my opponent frustrated and prone to mistakes, but lately I've been trying to just set up spikes and not stall/wall as usual before sweeping. Am I trying to sweep far to early? That may be the case, or just not getting used to my current team before fighting a tough opponent. Maybe I should just stick to one team before making alterations to the lineup, or try to find out more of my opponent and set up a team accordingly? Asking around about what someone uses though is far below my pride level, but finding weaker opponents now is just as hard.

I should just take the anime's advice and get back to basics and work with my strong points, but after such horrible losses I really dont want to battle most of the time... Anyways, enough of my depressing rant. I'm going to bed...