Infusion?

I have 3 sets of armor but I have not infusion them at all.

Do you need to ??

Only in the later mission of Prophecies, where you fight Jades and Mursatt who use the skill Spectral Agony.

http://gw.gamewikis.org/wiki/Spectral_Agony

as long as you stay away from mursaat you'll be fine.

My ranger has several sets of armor, and I infused about five of them. I later bought a set of Ancient in Nightfall that I didn't even think about infusing. Recently, I went into a Mursatt/Jade area skill capping and was fighting and killing Mursatt and Jades when it suddenly dawned on me that my armor wasn't infused and I wasn't dying.

Bug? Glitch? Or is infusing one set enough for the entire wardrobe? Or is armor from Elona naturally infused?

Your question is a very good one, Artfull.