Finally beat Medium Mode without any team members using coins for once. A team of Viking/Berserker, Tao/Medic (Me), Viking, and Treasure Hunter/Medic pretty much obliterated them. During Boss Matches, Vikings constantly knocked-down the monsters while the Treasure Hunter and I handled the boss with medium range distance. While the boss is down, we would cast Heal for a split second. Sadly, using the distraction with knockdowns cannot work in Hard Mode, because if you take too long, the Mini Reaper will come after you.
As for the Medium Mode main Reaper, it was all mob combos.
The one that I noticed which helped the most, is that the other team members focused on their cooldowns instead of their stats, so they had a higher chance of using a Skill to evade. I have to keep that in mind.