Well, waiting seems to be the least effective strategy, in my opinion! In the first round, we destroy one stack (usually the lower left one), while distracting/holding back the three stacks on the right. In the second round, we retreat only if we sense danger. It's usually difficult to take on 3-4 "canned" armies without magic. At least, you need to use a simple slow or bless spell. Although, Neo took the maximum reward for the swamp in the second week with his native troops without magic, if I'm not mistaken (he had a save somewhere on HP).

We need to be more specific here. A lot depends on how the hero is developed in the first week. There's a big difference between attacking a "canned" army with a level 3 hero or a level 7-10 hero :D