The start of battles doesn't necessarily decide everything. More accurately, if the opponent manages to quickly bring the battle to a logical conclusion, they will win. Literally just recently, I played Academy against Dungeon (there's some kind of same-old "Dungeonmania" epidemic lately 8^) ) where around the middle of the battle my position was depressing; everyone had died except for ~200 golems and ~50 gargoyles. He had almost no one left, though his ranks were heavily thinned, but the warlock's mana had run out, and golems are tough with infinite retaliation. The Drows died trying to destroy them (stone skin, strike, evasion, etc.). During this time, I summoned a phoenix that burned all the CDs (4 per turn), ressed gremlins who patched up the golems... The warlock saw victory slipping through his fingers... but what could the pointy-eared one do.
In general, Academy is probably the most difficult castle; the outcome of a battle can depend on a spell cast at the right or wrong time. And I guess the strength or weakness of castles should be proven on the battlefield)