I've got the shoulders/chest as both cloth and leather for each account.
Any caster type toon will wear the cloth (caster) BoA's, even if they're a shaman.
And any melee type will wear the leather (melee) BoA's, even if they're a plate toon.

As they level, the relevant stats and more importantly the experience boost outweighs any loss in armor.
With 4/5x a toon, it doesn't really matter, mobs die so quickly.
At the tail end of Hellfire, my 5x Hunters did the Cenarion Expedition quest where you plant a seed and kill the elite; it was the first crossbow upgrades offered by a quest reward.
It turns out they were using level 15 crossbows at this point, because I couldn't be bothered to level bows/guns.
Also turns out, they had not trained since 56th level.
But they had no issues with Hellfire, doing the entire zone (minus a few collections) in a few hours one evening (flying mounts help immensely).