Nah, there's a lot that can beat Aron. Poison, Burn, Hail, Ghost Pokemon, Steel Pokemon, Substitute, Multi Hit attacks, Mold Breaker, etc. It's only normal attacks that don't work against it. A well prepared team should have SOMETHING that can counter Aron.
Ninja'd 4 times over. I need to learn to type faster.
Also Rock and Ground pokemon, since they are immune to SS too. The main issue, however, is stopping Shell Bell from working, and that's why Steel/Rock/Ground can't beat it. You need a Ghost, Taunt, etc.
The other option, and the one i personally run, is TrickScarf. That gets rid of Shell Bell, so even if all things fail, you can still sac your TrickScarfer, and then the next pokemon can take out Aron with it's measly 1HP left.
My question: I run a TrickScarf Jirachi, which i love to use to cripple Burungeru. I find, though, i often outspeed Burungeru even after having tricked away my Scarf, in-game. I just forgot how many Speed EV's i run, and also how many a standard Burungeru would run competitively if any. So, if i want to outspeed after Trick, how many EV's do i need to outspeed the average Jellicent with Jirachi?