Alright I have completed a small round of evil NPC pwning here are my observations for the NPCs I faced to day in relation to Risk/Reward.
I started with the:
Gnolls : Since I last faced them in May, I noticed that some of the spawned Gnolls had very dangerous swing and as Mr. Cromwell said the reward is not worth the effort to travel to the northern woods (unless just for training) The main problem I saw with the gnolls was the amount of useless longswords they dropped. IMO longswords should be eliminated from the drops unless the quality is at least average or there is an NPC that would buy them. I do however like the food they drop very much, steaks are nice to bring back. Also I like the fact that they drop light loot making it easier to carry back to the merchants, like half leather legs and chain helmets but there worthless really to sell (5 copper for chain helmet, 10 or 15 for half leather legs). Your armor takes a good beating from the swords Gnolls use. But overall I see nothing too terribly off balance.... tis a long walk.
Bandits: Bandits really upset me.... I know they are weak and are for beginners but out of all the NPCs on the map these you would think logically would have gold. It can be said that no one goes by there to get robbed so they have no copper, but damn....they are truly a worthless NPC.... I killed three of them on my way to the goblins got nothing.... I know only three but I am faced them in tthe past and had more gold stole than looted

I kill the damn bandit and I cant even get my own gold back.....

I have no suggestions for this NPC other than delete its useless existence. (could have great potential and logic coin drops)
Goblins: I was very impressed with the risk/reward of goblins (didnt go to the peninsula only the abandoned ruins) they dropped decent copper for greedy little green bastards 9 coins give or take (candy as you call it) they also dropped ample arrows, leather boots, light hunting armor, and green robes: all which are sell able. They also dropped their short bows or slings which are useless really (think short bow can be sold in varshikar) and lamb legs (uncooked) can we at least cook them, I dont know many cooks that can cook lamb, but then again I just eat the steaks. The goblins also mounted a good attack on my character, fast little tykes. I dont believe the goblins are a bad choice for average fighters to loot but then again no fighter can really make a living off them....
Crypt Mummies : honestly could care lowest level monster NPC and relatively useless my mage character can kill them.... so dont care what they drop as long as entrails remain one of them. Wish other creatures did too (eg wolves, gnolls, trolls, or anything else with entrails

)
Crypt skeletons: Dont really care what you do with skeletons honestly as long as they are not the main source of income for fighters BORING! *chuckles* although I was highly unaware of the lonely skeleton in the lowest levels of the crypt, he dropped me some not so bad stuff: steel boots (Eliza's 25 copper), bluestone (Floro buys), a bastard sword (should be removed as a drop IMO too because useless weapon and unsellable), and finally 12 copper.
Ogres : At this point for an above average to good fighter going here with one other person will provide you with the best reward for your risk copper wise. Mages drop 20 copper roughly while the warriors drop some usable longswords. Sadly however I do think black coats, blue coats, or pipes are much use to a fighter or anyone rather. They dont drop anything of use really. I really think they need re-examining, like Oger said earlier some NPCs need to drop unique items that are needed by crafters that fighters can provide easier than they can procure. Easy example pure water for an ice blade or magical armor (smith) and for the carpenter for water wands ( I know these items are rare craft able goods). Or perhaps a Quest NPC that sends you on a wild adventure to find things only certain monsters have.
The last fiends I faced today pissed me off!!!
Red Demon Skeletons and the infamous Red Necromancer: this was the most disappointing Risk/Reward NPC that I faced. During May I could slay a demon skeleton alone using only one potion. (my skill may have decreased *shrugs*) Today was not the same two others and myself went to the graveyard to tackle the demon warriors and advance upon the Red Necromancer. There are two demon skeletons before you get to the necro to be clear. We started fighting the first one and after about 45 secs we killed the first one which dropped 20 coins and a corroded serinjah absolutely not worth killing those things for the amount of damage they do to your armor and weapons. Then we got to the second one after about 30 secs we killed him another 20 coppers and a good short sword ((clarify red demons use MAGICAL LONGSWORDS yet they drop short swords???)) absolutely not worth the risk to get a short sword when there are: serinjahs, longswords, poisoned blades, magical blades, broadswords, and anything better than a short sword. So then we all three tackle the red Necromancer:
Who summons at least 4 mage skeletons, can use his own magic, teleport to chase you, and he is as strong or stronger than the warriors in the end the strongest fighter out of us three was ghosted for 40 coppers and a good shortsword.