As my character is strong enough i have decided to try to fetch more figurines/cards to improve my very nice museum rank and decided to grind the "Party" missions, as you can kill the named important NPC without karma problems.
Though avoid killing those random nobles and tourists directly, as it gives a karma hit that will be annoying to access merchants, use Summon Monster and teleport away to let the monster kill those nobles/tourists, then get back and fetch the nice ores they leave behind.
But for named NPC, it's battle time. Though be sure your character is powerfull enough, because guys like Loyter and "Dwell in Vanity" are really powerfull on their own, but if you have some teleport + powerfull direct attack spell (magic dart is fun at high level) , you should be able to kite them to death.
I got several of the figurines/cards i wanted, and noticed that it's a good source of artifacts too, sometime one of the unique "rich" named guy (not noble, don't mistake them, you can kill those "rich" named NPC without karma problem) and some of the unique NPC can drop superb loot.
Now if you're trying to play with keeping your Fame high to unlock Panic/Challenge missions and high level Hunting ones, losing a Party mission result in a big Fame hit (more than 1000 fame each time).
I went from 55000 fame to 34000 after grinding those missions (and lost access to Challenge mission and the Hunting ones have lost several difficulty levels unfortunately and then reward).
Will take a while to get back that much lost fame.
The only good side is that from level 50/60 , the rogue ambush members are level 30/40 now and at my character status are not a problem at all anymore even without using teleporting.