I would level 5x Rogues, as a 5-boxer, over going with 4x Rogues.

You can "solo" in battlegrounds, with 5 toons for increased kill power.

If you have a higher druid already, then maybe 4x on other accounts.
Alternatively, level 4x rogue and 1x druid.
That way you have some heals and rez, to keep the team together.

I would arena as 4x rogues.
And get a friend to play their own healer.