To be honnest this troop placement doesn't make sense.
Maybe the guys from EC changed something but the Troop choice is much more important then how many you put in a specific slot.
Slot 1 and slot 2 are actually important. If your troops survive, the enemy cannot use the "free strike" from slot 4 and 5.
If you defeat slot 1 and 2 completely and slot 3 gained the upperhand in his challenge versus the opponents slot 3, your slot 4 and 5 can kill all remaining troops with "ZERO" losses.
I tested this a few times vs Dark Knights which are all mounted troops.
DRK Troops
[1] 98 Drk, [2] 2 Drk (lmao?), [3] 81 Drk, [4] 84 Drk, [5] 77 Drk
VS.
Kan's Troops
[1] 50 Heavy Cavalry, [2] 50 Heavy Cavalry, [3] 100 Pikeman, [4] 15 Horse Archers, [5] 15 Horse Archers
Result
DRK Troops
[1] 0 Drk, [2] 0 Drk , [3] 0 Drk, [4] 0 Drk, [5] 0 Drk
Kan's Troops
[1] 48 Heavy Cavalry, [2] 49 Heavy Cavalry, [3] 97 Pikeman, [4] 15 Horse Archers, [5] 21 Horse Archers
This was done with a Lv. 15 naked hero with no combat specs and the fight was 30 squares away, which basicly puts them at an equal level.
Seeing as all was done in just a single round it's safe to say that the Horse Archers butchered all the Dark Knights in slot 4 and 5 and prolly what was left in slot 1 and 2, since the Pikeman murdered their opponents.