I have been having SUPER bad luck with my warrior alt on a PVP server. She has a crappy level 13 2H and while leveling in WC and in the Barrens people were stating warriors should switch to dual wielding at level 20.
Is that a thing? Does it help with rage building issues?
If you’re having a rage issue, there are some runes plus some fury talents that help with it. There is Endless Rage and Blood Frenzy. Single-Minded Fury boosts physical damage while dual-wielding, but you’d have to choose that or Endless Rage.
I don’t really think they “should” as much as they “could”
2h should generally be all around superior to DW while leveling, especially since you don’t have hit-rate gear yet.
There’s the whole deep wounds builds, but idk if anyone is really using this outside of raids.
Been having the same issues, I’ve been suggesting that warriors be allowed to have duel wield of 1-handed weapons by lev 10 then be allowed to have titans grip by lev 20. I’ve tried all types of combinations and nothing is working for me. One reason I stopped playing a warrior. I’m also hoping blizzard reorganized the runes. we acquire several runes before we can actually use them. so this is useless to me at this point.
2h is better for leveling. dual wielding won’t save you 
Get 25 and get that ashenvale rep. You can get both a MH and OH from that.
Warriors that are running DW right now avoid that massive miss chance by using a /stopcasting macro with Heroic Strike and a swing timer. When HS is queued, that extra 19%(IIRC) miss chance from dual wielding is negated on your off-hand - the game reads your off-hand auto-attack as a special attack while it’s queued, and this was confirmed to be “working as intended” four years ago (Ctrl+F “Heroic Strike”) - so you queue HS, let your off-hand hit, /stopcasting before the HS goes off with your main hand swing.
It’s still probably smoother to level with a 2h weapon(especially if you’re averse to swing timers and macros), but it doesn’t require a ton of hit gear. You do still get that extra 19% miss chance with your main hand weapon’s white hits, so if you aren’t doing considerable damage with your off-hand weapon, you’re not generating a lot of rage with it.