I've checked the forums to see if it has been brought up before and I have studied some of my battles to make sure I'm not saying something already implemented, so here it goes...
I believe that our creatures should have a 'reach' which would make people have to use a mix of creatures in order to add importance to formation. It doesn't have to be complicated, could just go something like the following:
Aramors are pictured with swords and axes (even at the earlist levels) so their 'reach' would allow them to attack anyone in the front row of your opponents formation. Once the first row is destroyed they would then be able to attack the back row. This may mean to compensate they could be given more damage or more armour/hit points.
Archers really own at early levels, and naturally an archer would be able to 'reach' all enemy opponents. This could then be balanced with lower armour/hp or something on those lines. At the moment there are a lot of archers in the front row which isn't really 'good' battle strategy in practice.
If you wanted to go further you could say that 'hand-to-hand' creatures, if put in the back row wouldn't be able to attack until the creature immidiately in front of it (in the formation) had been killed. This would force a balance in peoples' formations between ranged and hand damage.
Powers, like Heal, will still be able to reach anyone as it is much like a ranged effect. Just thought it would balance battles a bit as at the moment any creature can attack any other.
Please note I am only MP3 at the moment, so if someone is further in the game and sees a big hole in my suggestion then of course you are in a better position to comment than me