Your spell power, in relation to their health will determine how hard they hit.
So the average item level, assuming you use appropriate gear for Lock pvp, will largely determine how powerful you are.
When gearing up, very geared opponents suck.

As a melee 5-boxer (ferals), a 5x Demonology boxer repeatedly owned my team.
He also owned any size group of opponents trying to get past him at the choke point he was holding.
We essentially both had mostly full honor gear, with the odd piece of arena gear here or there.

I'm pretty sure my DK team would have given a better run for the money, because of interrupts and the AoE nature of Howling Blast... cleave > non-cleave, when everyone is bunched up.

The majority of players are going to lose to you, in a BG situation.
It doesn't matter what you're playing... 4x/5x anything, is going to win quite often.
Especially if your team has some form of synergy.
Dots stack with each other, so that is fairly good synergy.
You'll have Agony, Corruption, UA or Immolation, which is fifteen dots in 3 GCD's...
You can macro tab, click, click, repeat... to quickly dot up a lot of opponents while on the move.

Look at the relevant strengths of a given composition and decide if you want to play that style.
Everything has things they're good at, which make them fun to play.