I miss random encounters from my long ago D&D days.
Some examples of what I'd like:
Scout char gets a mission from their faction leader to check out a frontier zone with four waypoints to travel to and click. With each waypoint there's a 1 in 6 chance of an encounter from a list e.g orc hunting party, or wolf pack come down from the mountains or whatever. When the scout approached the waypoint the die would roll and if successful the mobs would spawn at the waypoint. At this point the mission would change and instead of travelling to the other waypoints the mission would be to go back to faction leader and tell them about the mobs. When you tell them this triggers a mission / quest to kill those mobs. The scout char wouldn't have to take this mission it would just be a new one available that players could get off that quest giver. The scouting mission would go inactive until those mobs were cleared so the scout char might at least want to OOC that this new mission was available.
(My standard method for clearing these kinds of events is going to be once the encounter is triggered the mobs respawn normally on a timer unless all the mobs involved are dead at once i.e if there were four orcs in the hunting party then the encounter would clear if all four were dead at once.)
With random events like this you could have the same mission be different every time a player did it. Also once you had the mechanism and a list of possible random encounter tables you could always add a few more into the list to keep players surprised.
A second example could be a standard cave dungeon mission to kill chief bluglug with five caves joined by tunnels and with the first, third and last cave containing fixed groups of mobs with the toughest in the last cave. The second and fourth caves however could be random from a list e.g a die roll of 4-6 would be nothing and the cave would be empty, a roll of 2-3 would be 1-6 goblins and a roll of 1 would 2-12 goblins and a leader. The leader would be just a bigger goblin unless a second roll was also a 1 in which case he'd be a shaman unless a third roll was also a 1 in which case the leader would be a shaman plus a cave troll would come lumbering out of a shadowy bit of the cave a minute or so after the fight started :p
I'd love to be in a game fight like that where you're watching the group chat and suddenly someone says "oh **** they've got a cave troll!" lol
A third example could be crafting related e.g you have a mine with various shafts where players go to mine ore. Each time some ore was mined there'd be a low random chance of a rock elemental spawning through the wall. It would be easy enough for the mining player to get away but no one could mine there until the elemental was dealt with. I'd also have a rare random daily chance of some kind of goblin eruption. A model that looked like a tunnel entrance would be made visible in the mine and a load of goblins would come out. Again, mining would be messed up until the goblins were cleared.
These sort of things would make the world more interesting and i don't think they'd be particularly hard to code. In most cases they'd just be inactive spawn points that were triggered and closed via flags.
Adding randomness to the world would make it seem more alive.