I don't see anyone being successful in a 10-man Rated BG.

A 5-man often has issues in the 10-man BGs.
Less so, but still has issues in many of the 15-man BGs.
Having 50% (or 33%) of the team... always in one place, is a serious detriment.

RBGs are always 10-man.
If you had a pair of 5-boxers, you'd still likely be at a disadvantage compared to a ten individuals.
Even if the 5-boxers were almost always able to achieve objectives where they were at.

If you're all ten players, in a 10-man rated BG...
You're only going to efficiently play in one place at a time.
You might guard your flag room, so they cannot take your flag... but there's zero chance of capturing their flag, while also protecting your own... and once both flags are in play, your flag carrier will get stacking vulnerability debuffs until they're one-shot.
A single flag return for the other team, will win the game likely every time.

Any game where you have to protect 3 of the five nodes (or even 2 of the three) isn't going to be that good for you.
You'll have to split your team, and concentrate on two separate objectives at once.
The other side is free to leave a solo player to guard a node (and call out INCs).
If you don't split your toons, three solo players will hold more nodes than your entire boxed team.
If you do split your toons, you'll have to be able to manage two separate battles simultaneously.

Basically, to be at all competitive in a Rated BG, you're going to need at least three players controlling the ten toons on your side.
You'd likely be better off with as many individuals as possible.
I could see two 3-boxers and four inviduals, or something similar... as having a chance at some wins.



Non-rated BGs are going to be much more doable.
The opposition isn't always going to have good gearing, and if you do... your 3/4/5, might be able to win some games, if the rest of your team is half competent.

EotS can be won, by rushing towards whatever they hold... and taking it.
If the rest of your team is willing to guard what you take, with at least a token force.

WSG can be won, if you intercept their flag carrier consistently.
And your team is capable of returning a single flag carrier.



Most boxers go for IoC/AV, because multiple compositions have a chance.
Not everyone wants to play the most optimal (or close to the top) team.
If you prefer 5x Feral or 5x Rogues... you have a chance to contribute to a win, in a 40-man.
You're probably guaranteeing your team loses any Rated BG and most 10/15-man non-Rated BGs.

It is a large scale BG, so you're only 12.5% of the team... which is a huge plus, as every other objective can (in theory) be held by the rest of your team.

Essentially, you can play what you enjoy.
You get the strengths of boxing... blowing things up, or making anyone near you immune to damage via your healing...
And can still win, at least 50% of the time (often, far higher... if you concentrate on an objective or two like recapping bunkers/towers).