The most difficult alternative

it's easier to level them up using ranged and spellcasting units

A fast, demoralized griffin/air element/ifrit, etc., arrives – the heroes die a brave death, especially if there aren't enough genies to slow down and then block all the stacks of flying units.

Added 3 minutes later
2 shnurov_hl, by the way, can Haven afford to break through the Castle's defenses (1-2) in the first week? As long as there are enough hobbits and units to occupy the dragons for 1-2 rounds.