Maybe not much chance of a high rating, but if you really want to arena with a group of 5, it depends on your goals.
Intentional losses, or not trying very much, if you just want the points. Or don't even zone in, as mentioned above.

If you just want the pvp, and to do your best, for the fun of it.
Try to win every game, and as you lose your average match difficulty will go down.
As you improve (rating goes up), you play against stronger teams.
Eventually your rating averages out to your actual pvp skill with your actual toons; on peak times you'll mostly play similarly skilled teams.
The system tries to match you against teams near your rating when possible.
Play peak hours, on the day following maintenance and the day before maintenance so many more teams are active.

To play competitive with a goal of 1850+ (or insert other number), not sure that a 5's team, all controlled by 1 player, can do it.
Even still you can acquire points to be more competitive, for if they do change how arena is working.