Just play the 12 energy requirement and hope that you are lucky lets just hope that their next event is not like this

Not sure what the problem even is with this quest. I finished it pretty fast, faster than the "kill 200 of x monster" ones. Just do the normal one, not even sure y u would need to do hard since the event items cant be exchanged, doing the hard difficulty for more stam is dumb. 

The problem is it's an RNG treasure hunt for bosses, which can be completed quickly or turn into a energy sink nightmare. I would suggest cycling through the 3 difficulties to see if the boss appears and if not clear the stage that gives the best reward (catalyst, fodder, gold)vs energy usage 

I can only advice to go into Normal or Hard difficulty since (supposedly, as mentioned in other threads here) chances of goblin or scorpetra appearing are higher on these difficulties (no idea by how much). Also, to be honest, only finish this one if the normal enemies are something you are farming (kill X enemy for a connection or something)