This has been well-known since closed testing – I had already asked Praetorians like Superfluff to look at combos like the Flame Torrent + Raise Skeleton combo before AoM release, and other Praetorians like TomoDaK had also experimented with their own devotion combos with their test necros. This concept is explained in more detail as part of the “Special Topic: Devotions for Raise Skeletons (Necromancer Mastery)” section of the Pet Devotions for AoM guide. Here’s a portion of the article:
Refer to the article for additional information about cooldowns, AOE vs ranged restrictions, %WD, and lots more.