Fighter and barb are much stronger candidates for a pure melee build. A hybrid guardian can be very effective, but needs specialized and very high quality gear.
I'd really stick with a class that is meant for melee, or use the guardian as a healer tank.
I don't like the guadian class in general because they are worse healing than mages, and far worse melee than a fighter or barb. The only real advantage is that they can tank+ heal nicely with the right gear, or work as a nice hybrid with great gear.
These are my opinions about it, but I'd definately try to get more info from someone who has experimented a bit more with this class as well.
This post was edited by mwm_zyxcba on Jun 21 2009 11:22pm