This is a little trick has been around for a long time but hasn't had a purpose until recently.
I noticed quite some time ago when speccing from affliction to demonology that I didn't gain my MD bonus to the pet that I had out. I speculated that having a pet out when speccing out of demonology would have a similar effect, and it did. When I specced out of demonology I kept my MD bonus until my character had to be reloaded (i.e. can't change continents, enter instances, take a gryphon, enter BGs) It seemed pretty cool at the time, but nothing really nice because anytime you wanted to have MD with a different spec you'd have to spend 50g, not fun for something so limiting.
So I thought to myself with the expansion, "what if the same thing applies with the Felguard?" Sure enough it does, only better. Pets enter instances, cross continents, and enter BGs with you, If you are specced Felguard and respec out of Felguard, guess what. YOUR FELGUARD DOESN'T DESPAWN! While the MD bonus and SL bonus disappear when your game next has to load your character, your Felguard WILL stay with you. Since BGs automatically resummon your latest pet for you, as long as you never summon another pet, you can keep a Felguard with any spec! Though he won't be quite as powerful as a FG specced lock's.
This is what I have learned upon testing:
- If you or your Felguard dies outside of Battlegrounds, do not summon another pet. Just enter a BG and die, when you rez, you will have your Felguard back.
-You cannot enter an arena at all, as doing so unsummons your pet.
-SL and MD will stay as long as you never do any of the above mentioned. Meaning it would be very nice for going on a world PvP killing spree, but alliance is restricted to the Eastern Kingdoms because they have no lock trainers in Kalimdor. Horde can do either but must ride to wherever they intend to PvP. However the Felguard can go anywhere except on a gryphon/wind rider
-Unfortunately you lose your Demonic Knowledge buff and Fel Intellect and Fel Stamina buffs on your pet the instant you lose your talent poinst, the hp and mana just disappear off of you and your Felguard.
-NEVER SUMMON ANOTHER PET!
So there you have it, on PTR I am currently specced for unstable affliction but run with a Felguard in BGs while dotting and cursing, the extra stun is quite nice and I'm sure other warlocks are pretty pissed when they spend 8+ seconds trying to get my FG banished while I cast UA on them.