1:- just have it work on whether a mob is tagged by them in any way. (this is actually a bad idea because of casters but could probably be tweaked somehow) failing that just kick them or stand next to them till they get the hint.

2:- I wouldnt like this personally and i know a lot of my friends would hate it. maybe in matched groups it'd be acceptable. But in fixed parties definitrely NO. when my friends and I group together we usually split up and head in different directions to grab chests and clear a floor faster round up any aggroing mobs and melt them on the portal once weve got the chests. . so it would suck if i've gone south and got a silver and the guys that went north dont get it... because there more than one room away.

3:- same deal here as with number 1. stuff in potd hoh generally melts so fast casters would be at a continuous disadvantage... even with insta cast dots mobs would be dead befroe they even land a tick of damage..