So who wants the Dream Lord to appear again in S7?
No...The Dream Lord only worked because of the fact we didn't realise until the end of the episode that it was the Doctor...I think there's a thing in Doctor Who where "that villain was awesome, bring them back"
Like the Angels, the Dream Lord can't get better...
Exploring the Doctor's dark side though and have him see the Dream Lord's reflection when he does something dark? Absolutely!