I'd say it is the number (scarcity) of mobs in combination with when you run to look for them, you get screwed by running into melee bigger than you can stand.
I don't think its tuned well at all, maybe if you stay on maps well below your level, or else you are starting alt char and put rare items on him (or both).
I get quite a few of them but I ignore them totally by now, no interest, just press escape automatically when one pops up, because I know I couldn't do it, or I know there's too few mobs around to find them even when I can run about, so I don't even bother. Mobs numbers need to be increased or spawn times shortened a bit.
Not quite sure but I think I completed the quest several times in Oma caves but the reward was not worth it to keep trying, that's why I don't understand how some pple find them good and sort of rely on them when leveling.
Also I think the clock in mir runs way too fast ^^
And last, I started playing mir in 2001 because it was rpg like game, I ran away from arcade like game that fall (Red Moon). I don't like it much when you get tightly timed stuff in game like these kill chains.
Also I CBA with those bonuses I kept getting in oma caves (I think), like when you get the light above you and a sound like some roaring tiger when you killed a mob and you got like half a minute increased exp I think it was, I was lucky if I killed more than one mob with extra exp., either I couldn't find any at the moment, or I got too many mobs on me for my level and items and maybe had to run away or killing went too slow when I had another one or two mobs hitting me, that slows down the time to kill a mob too.
All in all, one big disappointment as far as quests go.