Put all of your points into Intelligence. Since Guardians have such high base vitality and intelligence the only smart way to make one is as a full on healer (and I think they're great to have as a catacombs character, everyone loves a great healer!)
Just find yourself a club + armour with nice heal mastery and a high EE heal charm and you should be good
that's really all there is to it.
This guide is a great help:
http://forums.d2jsp.org/index.php?showtopic=20473486&f=272