I realy think is a balance issue. I´ve player 2 heroes game, 3 heroes game and 4 heroes game. For the 2 Heroes is difficult for the heores, on 3 is quite balanced (at the beginning) and for 4 players it´s nearly impossible for the OL. With 4 Heroes on the table if each one of them manage to kill 1 minions, you will be looking to a table completely empty of minions by the begining of the 4th OL turn. And if you get experienced players, they will let one of them purposefully stationed on the spawning area.

My last play was Dead of Wing quest. Players won the first encounter, by the end of their first turn on the encounter all the elementals were dead and the Lnt on 2 Hearts away of dying. Then they decided to loot instead of finishing the encounter. So they calmly walked to every loot to search and spend the Guards turn just running away from the 2 dragons I´ve placed. At some point one of them killed one of the dragons just to slow me down a little more so they can loot the rest of the items without any worries. Even with the Lnt attacking every turn, it was futile. Even when I managed to deal enough damage to not be pittiful, the next turn came an attack and the rest of the tanker archer to recover all the 5 stamina he lost during his last round of monster attacks.

It was ridiculously easy for them, and it got even worst when they blocked the spawning area.

I think the bottom line is: Who ever thought that a few monster on the starting table and 2 more starting cards would be enough to balance the coming of 2 more herous, they items and their synergic habilities was completely triping.