Has anyone tried this tactic of not playing any overlord cards for the first encounter to hoard them for second encounter? Basically essentially throwing the first encounter to maximize the number of cards in your hand in preparation for second encounter. I wanted to know what everyone's thoughts on this type of OL tactic/behavior

I don't have a problem with it, personally.

Legal but not fun.

Personally I would never spend hours on a game and not have a blast with it and neither would any of my friends, so that tactic would probably put a sad ending to my Descent campaigns.

Instead I use the tactic to go for the goal. If I am loosing my players usually try to draw out the game so they can loot all the treasure on the map while I try to hinder them from doing so or stalling them so I can use those last rounds to stack up some cards for the next map.

I've only done it for 1 night so far and I seem to have a habbit of tossing cards whenever I get the opportunity lol  literally tossing them.   PITTRAP! *card toss at player*

I don't think hoarding them would be fun at all.