I looked around for an item database that had the wand's effect, and it came out to be -1 more hp/tick. I'm trying to find the souce again, but yeah it's not too spectacular.
Edit: Couldn't find the original source but here are two others that have the same claim (regarding the Dia enhancement anyway). I couldn't find anything in english so bear with me
http://www.finalfantasy11.jp/npc/npc.ph ... um=&check=
(seems to only enhance Cure4 & Cure5 potency; enhances Dia with -1 more hp/tick)
http://ameblo.jp/hargon/entry-10017198322.html
(this guy only had the Dia enhancement info posted; -1hp/tick also)