Rank 6 of Drain Soul was used as an example to illustrate the fact that even at its highest rank, it's still a woefully inadequate spell to do damage with.
There are also some who insist that Green Fire is not an issue that "real, raiding" warlocks care about. Yes, I understand that raiding is serious business and endgame warlocks are supposed to be single-minded shadowbolt-spamming machines. To the real, raiding warlocks out there, I'll quote this from my favorite movie this summer: "Why so serious?"
Now that we've got that out of the way, some of you may have noticed that I didn't address the escape mechanism portion of the wishlist. I'd figured that this topic was intriguing enough to warrant its own article and a look at probably the most interesting ability - in terms of Warlock mechanics - that we'll get in the expansion: Demonic Circle.