Marauder questions from a Newby :)

It usually comes down to using your judgment. Most of the time if you lose hate on something, you want to focus on getting it back. However, if it's very low on HP and it's not going to immediately kill the person it's targeting, you can probably let it go. Since you're a Marauder, if you're hitting 3+ monsters your best bet damage and enmity-wise will usually be to Overpower. You'll want to get the Maim buff up after establishing initial hate (one Overpower should do it, just make sure it hits everything). MRD/WAR is really strong in dungeons, so you don't have to overthink it too much.

Also remember that if monsters A and B are about to die, your DPS jobs probably aren't building that much enmity on monsters C, D, and E, so you can probably ignore them for a couple seconds once you've gotten an overpower or two on them. Healing hate is divided up among everything you're fighting, so if a heal would generate 1000 enmity, but you're fighting 5 monsters, it puts 200 on each of them.