No and yes.
You can "buff" PA with effects such as Enervating Field and Freezing Rain (-Resist), but that is the only way.
isnt that more just debuffing the npcs not buffing the pa's
The only damage buff that affects PA other than regular enhancement slotting is the Build Up proc from Soulbound Allegiance.
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isnt that more just debuffing the npcs not buffing the pa's
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Which is why I said "buff" in quotation marks 
Anyway, that's why I like -Resist debuffs in my Illusion secondaries.
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You can "buff" PA with effects such as Enervating Field and Freezing Rain (-Resist), but that is the only way.
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This.
This is why Illusion is traditioanly paired with sets that have significant offensive debuffs (debuffs that make your opponents easier to deal damage to; notably -resistance). The synergy is quite potant. Of course, in the case of some sets (radiation) there are other synergies as well, but this is a significant one.
Note that PA CAN (unless Im mistaken - whcih is always possible; I havent tested it) recieve a boost from the %chance for build up proc in the ultra-rare pets set if it is slotted into PA itself and procs.
What's particularly nice about Soulbound in PA is that if it procs on any of them, they all build up.
QR
Weatherby_Goode - "Heck, Carrion Creepers negates the knockdown from Carrion Creepers."
-res debuffs and +damage buffs work on the same scaler. Both add damage to the natural cap of the AT. Both basically serve the same function. Since PA can't be buffed -res will damage cap them as effectively as FS would in a perfect world.
The subject says it all but... Do damage buffs from set bonuses increase the damage that Phantom Army does? I'm curious and can't tell from Mids.
And on a side note, I stuck a damage proc in Spectral Terror and I'm pretty certain that it works. I even switched to my second build to test it out but I just want to be sure I'm not imagining things.