Hello to whoever is reading this! 
I am currently playing a Shaman utilising the Boardman’s Plank set item, which makes the Storm Totem interact with both my (unique) companion, and myself. However, after not noticing any of its effects explicitly working, I decided to look a bit closer, and none of them seem to.
More precisely, here are the conclusions I came to related to each of its stats:
- “21% chance to summon a Storm Totem on hit with Tempest Strike”: After hitting the End of Time dummy 50 times and running a whole boss fight with Tempest Strike, probably amounting to around 100 or 150 strikes total, I didn’t see a single totem spawn, so I am fairly sure this doesn’t apply.
- “+21 lightning damage to spells and attacks when you are hit by lightning from Storm Totem for 4 seconds”: The damage buff should be strongly noticeable (a total of 63 lightning damage to spells and attacks, at 3 stacks, is pretty consequent), but I didn’t notice it at all. Also, I do not get any buff icon in the buff bar above the skills bar, but some other buffs do not appear there, so I cannot be absolutely sure it isn’t working.
- “+75% physical resistance to allies nearby Storm Totem”: I do not get the physical resistance buff, even though I do get the elemental resistance buff that comes from the Shaman mastery passive. I haven’t found a way to check for certain if my companion gets the resistance buff, but considering how the item is worded, I assume I should get the buff as well.
- “Your companions are enraged when hit by your Storm Totem”: This mod is tricky to test for sure, because 1) I haven’t yet found a way to make the Storm Totem attack the dummy, which means I could only test that against actual enemies, and 2) the buff granted to the companion is attack, cast, and movement speed, which isn’t completely obvious to spot when in the middle of an actual fight, but even in the boss fight I mentioned before, which I ran with the set item, a Storm Totem (which I summoned myself near the end of the fight, after testing its ability to spawn on Tempest Strike hit), and a companion, I didn’t notice any speed change on it.
Here are the screenshots of my resistances without the Storm Totem, and with the Storm Totem. I would have liked to run some similar tests with the other set items, which also grant buffs related to the Storm Totem and our companion, but unfortunately I haven’t found them yet.
I am also including my system information, even though it didn’t really seem relevant (if the game logs are needed, let me know and I will join them as well):
DxDiag.zip (20.4 KB)
I hope I gave enough information; if I can do anything else, please let me know. Thank you and have a nice day!