I played some other expansions for many years and want to start a new challenge. Legendaries and pve-items destroyed a large part in wotlk, cata or legion, that's why I'm interested for 70 and not for level 80 pvp. Are bgs and arena active at level 70 on Icecrown?
It doesn´t matter what low level pvp bracket you play it is always the same outcome. 100% pimped chars oneshotting everyone who is not 100% pimped. Depending on which level range you play, there is always this 1 or 2 classes that are extreme op. With 3.3.5 patch, at lvl 70 dk and prot war are very powerfull.
As Mercy said a 70 Glavie'd rogue (even some fury 1 handed warr) can obliterate even 80s in mere seconds. Almost every BiS (or even close to BiS) melees can destroy level 80s even some WFs if stars align.
Gearing up most of these classes is fairly simple since you can do insane dps even at no resilience with the PvE gear going glass cannon. There BGs somewhat possibly more after the cross realm gets released.
Arenas and S4 is unfortunately broken since there's no S4 vendor and nobody under 80 can create nor join an arena team. So Brutal, and other arena sets are unavailable.
The 3 guilds are <Carried> (70-79s) to <| Challenger |> (full 70s) on Ally and <Young Brutal Beautiful> (70-79) on horde.