Right now I’m operating under the assumption that Enchantress is going to generally be the best. First, a question though: are you using an immortality token? Or the one that gives follower skill cooldown?
If you’re not using immortality, then whatever follower you take, you’ll want them to be augged out the wazoo, have them equipped with Esoteric and Mutilation Guard (these two gems, on the PTR anyway, did work with follower) and you may also want to run with War Cry, for the extra follower defense. If you are using an immortality token, you can disregard all that.
As far as CDR is concerned, the Maxroll guys reported that sheet CDR was not working at all on followers, with one exception: the Templar’s “Heal” ability. That alone would be enough to warrant taking a bunch of CDR with Templar, since getting extra healing with this build is very helpful. Then again, that may have been a PTR bug, one way or the other, i.e. CDR may have been supposed to work on everything, or on nothing- not just on that one ability.
But anyway, back to Enchantress: I am, for now, assuming she’ll be best. If you are in need of CDR, then take her CDR ability. This will generally be the case for setups not running Gogok. Or if you are running Gogok, take the +elemental%. In addition, take Erosion for +10% dibs, and her cheat death. If possible, don’t take either ability from the first tier, but if necessary, take Charm, as her Temporal Pulse ability slows down too many enemies too often, and makes it really hard to get good grouping.
Speaking of which, just taking the Enchantress at all makes it harder to group enemies, since she runs all over the place, rather than standing in one spot, like the Templar. But, her abilities are just more essential for this build, so I think she’ll be the way to go. In terms of gearing, take an Oculus Ring, Krede’s Flame, Nemesis Bracers, FoT, and Homing Pads, and make sure she’s at 25k+ INT. The rest doesn’t really matter.
As for Scoundrel, I think he would also be a fine choice, particularly if you’re using Gogok and don’t need the extra CDR. But, I think the Maxroll guys are perhaps overvaluing his CHC bonuses. For one thing, his cloud ability only has around 17% uptime. For another, there’s no guarantee he’ll deploy it in the right place. Taking his cloud prevents you from taking his cheat death. And he’ll run around and make grouping harder just as much as the Enchantress.
Anyway, those are my thoughts at this moment. I’ll update them as I play more.