On a second time I would more easily be able to do so yes, but realize the level for persons not being you is a big unknown, and I was in a big rush because of the message that said 'hero parties are already on the way'. I just scouted the west dungeons with my reaper, but simply assumed going north was not an option and thought I had to quickly take over the east dungeon before the parties would come. And a lvl2 reaper just can't take on two knights and all those other heroes.
Another option would be to just tweak the initial objective - don't talk about the hero parties just jet, but only give that information when the portal is claimed and the timer for the parties start. This will give the player more time to think about the level before starting out for real, making it more manageable. What I've seen so far is that you make good maps with lots going on, so players need time to take it all in.
EDIT:
Completed lvl5-Exorcism. Simple but fun map, it works. I went about it with little trouble, and it is a nice pallet cleanser after the last map. At the end I almost lost, as gold had been abundant but I suddenly found myself short on cash after the increasingly expensive paydays and I still had destroy walls to cast with no more gold available and the gems also behind the walls. Selling some rooms put me over the line towards the needed cash and an easy kill of the avatar.