I have not leveled my hunters by doing dungeons. If you really like doing dungeons instead of just doing the regular quests outdoors, leveling 5 dps might be less fun.
If your team cannot queue and fill all roles (3 dps, 1 tank, 1 healer) you cannot use the groupfinder to enter any dungeon you want. Then you have to physically walk to the dungeon. If you have 5 paladins for example they all have the "possibility" to play as all 3 roles, and can therefore queue as a full group.
And even if you do that, I'm sorry to say that I have no idea how x5 hunters perform at lower levels. I leveled some of mine by questing, and some with the free lvl 100 boost which came with some xpac purchase.