Found that healing and armor are useless on a 2 man team. I can make it farther with a pure health tank and pure damage. That would change on a 3 man team, but you don't get enough stat points to make either one of those stats useful on a two hero. Been running the game for 2 hours and can't make it past floor 13.
What's the points of the permanent bonus of the LVL III investment? By the time I am high enough level to run it I already own everything. Do the bonuses persist through reset?