We are playing on "Ragefire" which is a TLP server. Old content like this has renewed interest.
Recently we acquired the Orb of Swarming Darkness (OSD) by doing DoN missions. OSD has the focus "Minion of Darkness" (MoD).
TSS was releasing soon (we'd been away for a while) and I wondered if it would work on the new pets. There were mixed reviews but this post has comment about both the high and low ends.
First off, I'd like to greatly thank Adonhiram for a posting on the Magician's Tower discussing a lot of details about how pet foci work. In the article "PET FOCI IN EARLY EXPANSIONS Part I, how they work" he states that it is the level of the spell NOT the level of the pet that matters (opposite of what is stated above).
As a mage, I can easily test this. This is not to say that it works the same for other classes of pets as I've seen much posted by Necs and Bsts that contradict some of what Adonhiram said for mages. For a MAGE pet, Adonhiram is correct.
To test the minimum pet level was easy. I cast a 48 Earth Pet using my level 57 spell. According Whiteowl, the 48 should not focus, according to Adonhiram, it should.
It did focus. Cast w/o the MoD, the pet conned level 48. Cast with the focus, it conned level 50.
For the maximum level, that was more difficult. Adonhiram stated that, if it works on TSS (spell levels 71-74; Pet's all level 70) it is very slight. What is completely obvious is (and stated in the article) that it does not increase the pet level. Both the unfocused and focused pets are 70s. What is less clear is the hidden stats like accuracy and such. It would take some long parse runs to tell. The nuke portion of pet damage doesn't change (we ran focused and unfocused pets side by side).
The melee portion of pet damage is less clear. In a joint fights with both focused and unfocused pets (two of each) you couldn't tell any difference. If there is a difference it is small just as Adonhiram stated. Personally I'm no longer bothering to equip it to cast my TSS pets.
PET POWER: Again according to Adonhiram, Pet Power means NOTHING mathematical. Rather it represents a unique (based on pet focus effect) column in a DataBase from which to pull a pet model. The pet models are prepared by the Devs. Pet Power is nothing more than a number that essentially means "pet models focused by MoD" and nothing else. The models are what the devs decide and they've made a least one mistake in the past that proves it isn't mathematically calculated (a particular focused pet in a series was worse than unfocused).