That same concept applies to all aspects of your character. While you may have made something work for leveling, you’ll now want to fine-tune it to get the most from your character. You might notice a distinct difference between a level 1 character and a level 60 character, but you’ll also be able to distinguish between a fresh level 60 warrior and a fully-optimized level 60 warrior. The optimized warrior will survive for much longer, and will deal far more DPS!
Hit Cap to 8% – The utmost priority lies with raising your hit cap to a minimum of 8%. If you’re dual-wielding, the hit cap is actually 27%, but that value is almost impossible to reach, especially if you’ve just reached level 60. With that in mind, your special abilities (think rotational abilities like Bloodthirst and Whirlwind) only require 8% to actually hit. This does mean that as a dual-wielding fury warrior, you will miss auto attacks, but all of your special abilities that consume rage will hit.
Critical Strike – After reaching the soft hit cap of 8%, you’ll want to stack as much critical strike as possible! Critical strikes are helpful to any class, but warriors in particular benefit from talents that make crits even more important. 2 points in Impale will increase the damage of critical strikes by 20%, while 5 points in Flurry allow you to gain a 30% attack speed bonus to your next 3 swings after you’ve actually landed a crit.

...but, in my experiences, I found dual wielding to be fine, but only if you're Fury. I found that having two weapon swings meant having twice as many chances to crit, which led to lots more Flurry procs. At level 50 with two blue 1h swords, my kill speed was just about the same as when I used an epic 2h axe. And I wasn't even specced into the offhand damage talent. If I got a good string of crits, I could smack mobs down in 15-20 seconds, and easily hit Bloodthirst every time it came off CD.
The vanilla WoW Horde leveling guide you see on this site was originally made back in 2006 by Joana (AKA Mancow, or FuriousPaul).  The guides have been tweaked many times over the years to make things "faster".  The leveling guides were made because of all the messages I got from people asking me how I was able to level up so quickly on new realms.  I was first to level 60 on 7 different realms (3 with Mancow and 4 with Joana), even winning Blizzard's "First to Level 50" contest they held back in 2006.