Common loot drops needs to come down. With the current loot generation your backpack fills with to much common stuff that has to be thrown out.
Backpack and chest space needs to be compatiable. Currently it is very difficult to sort the backpack, craft things, or just know what you have.
Alot of the single player stuff doesnt happen/ doesnt work right in multiplayer, such as naga attack annamation, warrior charge not stopping at first target, more as I find them
Balance / Gameplay changes
Instead of Int, Wis should be the stat that adds to bonus elemental damage on weapons. This will make it so all three classes can benifit from the extra damage with out using points in a cross class stat.
The warrior needs longer cooldown on charge, or increase the mana cost. Currently with the charge ability is to powerfull in early levels. It also allows the warror to move faster than the other classes with little drawback.
The ranger needs a little rework. Tripleshot, tho a good idea doesnt work in minecraft. Replacing tripleshot with an ability that increases accurcy and range for mana is a great idea. The lightning shot needs to be replace with bonus lighning damage, or fire damage, it makes little since that a ranger would summon lighning bolts, the mage already does.
The mage is in a good place, and if wisdom becomes the stat for bonus elemental damage it will bring down the mages non spell damage.