My suggested formation is basically
T M Ae
Mi Ar
Ang
Basically a reverse pyramid.
By the nature of movement, most attacks will come from the front; We are moving in that direction. People coming in the rear have to catch up with us. So logically they must be running if we are walking. Have you seen the stealth penalty if you move fast? Even with our lousy perception, we'll hear them coming more often than not.
Also, Angel has 30 hp. One more than Mal! If the worst happen, she'll survive at least one round. Then we are just 4 square away in my scheme. One round and we have reversed the formation. There is no real reason to thin the front by 33% to account for the occasional lurkers. It'll put us at an early disadvantae for the vast majority of encounters in exhcange for a favorable situation in a minority of them.
Considering Teslay ; the reasons for him being in front are so elementary AFAIK that if I am overruled and we decide to put a defender in the rear, It's Mal that will go in the back and Teslayn in the front.
It would annoy the heck out of me to have to hustle to the front 95% of each first rounds, but I'll do it. Placing Teslayn in the best breathing spot is that important IMO.
He does a 5X5 breath as a minor action. This the best possible opening gambit we have against any group that includes minions and it's pretty good the rest of the time. But there is one obvious truth; we don't always win initiative and Tes (like Mal) has a speed of 5.
If he's stuck in the back, even if he wins initiative, he might be forced to swap a standard action for another move to get in good position. That would suck ; Breath + Attack is what we really want, mot just breath.
More importantly, if he loses initiative to the minion, then they are likely to swarm us and with a thinner front, they'll start wrapping around. Then Tes can't get as many targets without hitting the rest of us.
See :
4 minions, 3 man front
Mi Mi Mi Mi
T M A
Remember that flat footed doesn't really exist. Some classes like rogue get an edge when they act first, but the defenders threat area is still effective even before they act. So a three man front keeps a wider line.
Tes might catch them all or at least 3 of them without endangering any of the others.
4 Minions, 2 man front
Mi Mi
Mi Ma Ae Mi
Now the minions act first and start wrapping around. How does Tes catch lots of minions without spitting acid all over Mal and Aelek one he hustle up to the front?
He can't.
Tes in front. It's 2+2. If you want to go with Arden scheme of 1 defender in the back, then it'll be Mal. In that case we sacrifice Mal's ability to stop a moving skirmisher who accepts an AoO to move through the line, but it's a lesser evil.
Trust my limited experience in 4e ; these minions must go down fast. They are not just a nuisance, they do real damage that adds up quick.
EDIT : Well, these 'graphs' sucsk. Basically the pyramid should be balanced and the spread of these minions is all wrong but I hope you get the idea.