using Larimar to take Heal % off of a Map would help a lot in killing Legend and Mythic Monsters.
Legend (Red) and Eternal (Green) Maps only have the loot affixes. Gold Find, Luck, Item Quantity, Crystal Rarity, Myth Stone Rarity, 3x Golden Chests (6x for Eternal). so these maps don’t have Heal for monsters. I don’t know if Monsters can heal if there isn’t Heal % Per Second on the map or Heal % DMG on Hit.
Epic, Legend, and Mythic Monsters might have some healing ability of their own different from map affixes, but we would need to hear from @tdaniel or one of the other Devs to be sure either way.
the problem is that they could have so many HP compared to the damage you are doing that it might look like you aren’t doing much damage to them. so it might take some time to actually kill them. that is why Crushing Blow, and even more, Crushing Blow with Crushing Flames is so powerful. you might be doing 100 Billion DPS, but if the monster has a 1 with a billion zeroes in HP, it is going to take some time to kill it only doing 100 Billion damage a second. you are only taking off 11 zeroes a second off of a Billion zeroes of HP. with Crushing Blow, the first hit would take off 100 million zeroes compared to your 11 zeroes, and with Crushing Flames (5), the first hit would be taking off 350 million zeroes of HP compared to your 11, or the 100 of just Crushing Blow.
hope this helps.