I certainly agree with all the OPs, theirs are very valid points. While not offering a solution, I'd like to ask: What's a mongbat's purpose? Why is it there? Do you remember being afraid of one, or having died by it's hand? Ever run from a lizard man, troll, or old school earth elemental? What about as of lately, whaa... not afraid anymore?
Altho there aren't levels in UO, I think players hit levels where they quit being afraid of the monster under the bed, and challenge the one in the closet. Just as a child says I'm a Big Boy, or I want to try it without the training wheels, it's a move to that next level. Those are the days we remember, the Kodak moments, it was fun! And the adrenalin flowed. But that doesn't last forever, so we move ever onward in search of the thrill, that next level. One by one our mobs fall silent, but what of the plight of those before us? Those whose mongbat's bones have long blown away scattered into dust? What 'level' are they on? What horrors do they face?
I think that's the challenge a Dev faces, delivering the challenges, that next level. Offering content events/arc, and having it playable and enjoyed by a wide majority of players. So is there going to be really hard stuff in UO, yes, hopefully forever.
Allow me to [OT] a moment to speak of my Lockpicker, who learned the ways of swords and dragon slaying, in Destard, first wyverns, then drakes, and finally dragons themselves. The introduction of Greaters, that next level, while completely necessary, ruined my playground, I don't go there anymore. The north room in Destard could have been used to spawn Greaters, preserving the 'levels' of younger players.
Many have never even been in there, but it's a quite large area. Good idea, good intentions, implemented incorrectly and without consideration of many players. The current story event is no exception as killing a special blood elemental is the minimum requirement for entry. What of those who are thrilled just to watch from the sidelines, helping modestly when they can? Those on the lower levels, the youngsters, are excluded, and even physically blocked off from content. I see it as a trend, and there are plenty more examples, that while not physically blocking off players with boulders, players are none the less being blocked from more and more areas. Eventually, their next thrill will be in Non-UO content.