I would like to clarify some issues, which might be of interest to people doing this.
1. You need to kill the first mini-boss by hand, if you are a clothie, as the bot will simply fail at this fight.
2. Pets do not affect the rate at which you gather Lovely Charms. Tested and confirmed with a Felguard doing all the killing. You still get charms.
3. Regular is perfectly fine. I certainly wouldn't try Heroic as I am a clothie and am not even sure if on Heroic the Slag will give better yield of Charms.
4. You can totally AFK this, as once your toon is inside The Iron Crucible, there isn't much for it to mess up. You will spend some long sweet times with the lovely, charming Slag elementals and that's about it.
5. Yes, ARelog would be wise to use if you are gonna farm all day, as the GM's systems will be keeping an eye on your toon in the absence of other players, since instance farming is not really a new concept.
6. Get a half-decent CC with strong AoE capabilities. Things will go so much better for you.
7. Doable for any class.
8. Hellfire fans beware. Bring refreshments with you, because Singular might not always wait for your toon to finish channeling Soul Harvest and you may die. Yes, Singular + Hellfire is the best way to farm these guys fast. Prince of Darkness is the next best Lock CC. FelMaster seems to be messy and Zerfall is just slow. Really.