Are you looking for a build to be better in PvP with your Guardian? I currently have a level 38 Guardian and the best build I have found for PvP is a Defense tree build. However, it isn't as effective in PvE; therefore, I won't use it until I hit 50 since I need the DPS for leveling purposes. Meanwhile, if you're looking for a good all around build, I currently am using middle tree (the name leaves me for some reason) build. Let me know if you need exact points, seems to be pretty successful in PvE, although PvP I tend to be a bit squishy.
dioko