I am not sure why up are having trouble but where is an easy tactic, was repositioning some of the minis when you have 10ish seconds left to save some health and pick up coins from already damaged bugs.
1)round 1 easy, 1 goblin, you will lose health but live.
2)round 2 easy, 1 goblin, plus 1Orc for health, would should not lose health now since you have heal as well.
3)round 3 med, get atleast 1 poison rogue and put them right at the start
4)round 4-5 med or hard, based on your random pulls and coin, you should be able to get paladins + Poison. these do a lot of damage its best to position them at the very start, mid and just before the last turn to max out "poison" time