Just did a quick solo run through again to check changes.
Health can still be reduced a little bit (see my last post).
The attackspeed for the melee/MVP are too low, the melee one needs to be brought up, it actually has an array of skills it's just they come up so infrequently. The MVP seems to be in a similar position.
I think the melee one has Shattering Strike, but I tanked it for a while and didnt have anything broken, it may need specific weapon/armor skills to work properly (you could make it cast shattering strike for the animation then give it a small cast time for an armor/shield/weapon break to give players time to swap items off to avoid losing them).
The caster may outstrip the scariness of the other monsters right now, I feel like it's probably okay though as they can be a focus for players.
The MVP still seems to be going into passive mode, is there any of the AI left over in it swapping its monster type around in passive state? It's health is pretty enormous and alone it's not much of a threat right now, you could consider making it spawn with one of each ranged/melee/caster adds and have it summon a new set every 25%. A well geared group could probably ignore one set, but two-three could be tough.
Also as an aside, they may need something to do on rude attack, it's less of a problem for the caster and ranged dude, but icewalling/fibering the MVP/melee could be a strong way to help handle adds or kill them without consequence. Making them do something fairly extreme on rude attack would be interesting (instead of teleporting, forcing players to deal with anything extra they pulll is a good approach imo).
I cannot comment on the drops as I still havent seen anything drop except the white potion box from the first trip down there. However I strongly suggest you consider adding an empty bottle box instead of the white potions, white potions for slims are one of the last remaining zeny sinks left on the server and empty bottles are the last bottable supply required by players, even moreso now that you have fixed the empty bottle merchant.
It would be nice to see them gain the proposed sprites and a new map.