(unless you include minibosses, in which case the bats and faeries might need rebalancing)
Bear in mind that the little fairies that are shot by the big fairies are actually projectiles rather than monsters for this purpose.
But yea, the melee-only bosses (vampire bats, iirc) would not fit neatly into this little scheme.
I'm thinking that if I try this it will be as an alternate model that some monsters use; namely the miniboss skelebot, the miniboss amoebas, and maybe a few others: the ones where it seems to make the most obvious sense. Because if it doesn't work for a giant amoeba it needs to be reworked (or ditched in favor of something else) before being applied to much else anyway.
Someone up here mentioned Terraria, and Terraria is pulling its own problems as far as multiplayer goes. In any case where there is a high lag you'll have monsters "popping" around, which is honestly not such a bad thing, since they do this for ALL characters in play. But it does make certain skillshots difficult, especially in very high lag situations (200ms+) where monsters can entirely bypass you if you hit them in melee.
Thank you for clarifying that, I've only played the very beginning parts of Terraria and wasn't sure if they were really managing all that massive laser pew-pew in MP with none of the restrictions we've seen elsewhere. So they haven't defeated physics after all
They go for lag-compensation rather than local-sim-of-monsters, so you can miss stuff that you would have hit if you were playing singleplayer, etc. Not arguing that that is worse than what we have, just observing.
One thing about the "server-plots-a-course" approach is that I _think_ we can maintain the local-sim-of-monsters for the actual firing of their projectiles and the collision check for your projectiles so that we can still avoid missing when you wouldn't have missed in SP and getting hit when you wouldn't have gotten hit in SP. The thing is that the enemies would still be in _slightly_ different positions between the various clients, but it would probably be close enough that you wouldn't notice except through deliberate scrutiny.
The downside is that it's not compatible with some of the behaviors of our current monsters like bats making split-second direction changes to chase a rapidly moving player. I'm not sure, but my recollection of Terraria doesn't include anything like that: the slimes and underground-worms had fairly large delays between hops, the zombies would chase you but still had fairly relaxed changes in acceleration, etc.