Peacemaker is difficult, a dungeon-runner in my room said he did the thing 10 times with no Peacemaker.
Gardosen's seem pretty easy, I did one run and got one first try.
Basilisk's seems like an ass too...
Mini-Fire Golems are ridiculously easy, probably 100% drop, each Mini-Fire Golem I've killed dropped it.
As for PvP Medals...
Sucks for PvE'rs, uber for PvP'rs