What they should do is rolling need automatically binds the item to the winner, whereas with greed it could stay bind on equip. That way, if he rolls on your wizard loot, at least he gets nothing out of it, cant AH it. Of course, the need button on class specific items should be grayed out for classes the item isn't usable…
I was under the impression the store bought companions would be claimable on all characters of the account. At 20$ or more for a companion, this should be the case.
It happens all the time to people in my groups too, it isnt just me its talked about in /zone chat as well. And its not a computer issue, i could run 4 copies of this game at the same time and have 0 lag.
Yup threatening rush combined with enhanced mark is great for aggron I havent had much issues either, although my choices of dailys/encounters/class features differ a bit from.you.