The suggestions seem pretty consistent across the board that you would slot a ruby in the helm for other followers besides the Templar (diamond) for the obvious CD benefits that he gets. So I was wondering if that's intentional or if it's meaning to suggest the newer Hellfire Ring. The solo GR speed farm Enchantress currently links to the old Hellfire Ring of Intelligence. The new Hellfire Rings aren't guaranteed to have a specific stat, and the effect it different. The recipe is still there but the mats required only drop from the level 60 uberbosses, and I don't think you can even get into them anymore before 70, unless someone doesn't have the expansion I guess. The level 70 Hellfire Ring is craftable but the old patterns, Hellfire Ring of Intelligence/Dexterity/Strength/Vitality, are not. I'd think there'd be something more useful to be thought of than 0.45% extra XP or whatever. I do wonder why you'd bother with it, though.It give 45% XP, so 4.5% at level 70, and I thought XP boosts were only partially transfered from follower to character, so it's even less.

Apparently you missed it? The Hellfire ring is still perfectly craftable, just buy the plan from Act II and get the items from the Uberbosses, just like for the Hellfire Amulet.

Icyveins diablo 3 follower builds