You won't be as effective at 71st as you will at 80th.
That's a given.

However, if you feel like being there, there's nothing wrong with being there.
I'm personally going to take my mixed team there, as soon as I boost my mage to 71st.
The team will be 75 Boomkin, 74 Shd Priest, 73 Elem Shaman, 71 Warlock, 71 Mage.
They'll be there as a unit, until the last one hits 80.

In odd world pvp, people have frequently posted upper 60's taking out solo 80's.
Unlike PvE, your spells will land a lot more frequently vs players then they would against mobs.
With five focusing on one target at a time, you're a threat at 71st.
Just don't be too upset, with the AoE or someone killing you fairly easily.
You're low level, so die fast. But there are five of you, so similarly you kill easily too.

As long as you're not AFKing.
Or working weapon skills on the Rams..
You're not leaching Exp's