to point 5: when one player flees he can easily heal himselfand buy new healthpotions and then agian join the fight because he can run around in realtime while the other one is in TB-combat. that would make all bosses just boring since you can flee with one character and heal himself with no penalty at all.i think when both flee the enemys will regenerate.
this is the same problem that i have with the teleport pyramids i think they are overpowered when one is in TB combat and the other one can just teleport away.

to the point 1 i think is not good since there is no cover-system it is unnecssary. I think in D:OS it will be logical what is blocking when you are standing at a specific apot.

Point 2 like Singbird
Point 3 didnt they already implemented it? i thought so but i am really not sure.
point 4 yeah some tank abilities would be cool.