the PTR patch notes for patch 3.1 listed in MMO Champion features a lot of changes for locks in all their talent trees. There are some cool changes and a lot nerfs in other areas. But right now I want to talk about the demonology talent Demonic Sacrifice because when the patch rolls in, we won't see it anymore.
According to the patch notes, Demonic Sacrifice will be removed from the game. Obviously the patch notes are incomplete since we still don't know what's replacing it, even if some new talents have been revealed. This is sort of the same fate of the paladin talent Blessing of Kings (which will be made trainable in the patch) and still no announcement of what will take its place.
The removal of Demonic Sacrifice from the game is a bit of a toss-up for me. On one hand, a lot of Demo warlocks didn't take the talent anymore since it seemed like having your demon up is nice even in dungeons because of the buffs from Master Demonologist and Demonic Empowerment. Keeping your pet up has been made easier by the new Fel Synergey talent which was moved to the first tier and has a 100% at max rank to heal your demon by 30% of damage you deal. It doesn't help the cause that Destruction warlcoks like having their imp out because of the increased crit chance given by Empowered Imp.
On the other hand, Demonic Sacrifice was introduced to the game to allow warlocks put their demons to good use when they're better off gone than there. As I stated above, perhaps this thinking is obsolete but there could be instances when it could still be useful. The most obvious one I could think of is the Heigan dance in Naxx where a pet could be at high risk of dying and thus be off no use to the raid, so a sacrificed demon would probably be better. Perhaps the Sapphiron fight is also another instance where it's better to have a sacced pet because of the air phases where you need to get behind an iceblock or die.
Well no matter what you think about the talent, it's no question that it was a cool concept while it lasted and I hope that it's replacement will be something just as cool and hopefully something that could be an integral part of a demo build and others like destruction as well.