I only have a 23 Ranger, so I’m still learning the ropes, but I do have a level 80 Guardian and can tell you that Guardian DPS dramatically changes based on spec, gear and playstyle.
So far the best mix of survivability + DPS that I’ve found with the guardian has been Sword+Torch, and at higher levels (or in dungeons) survivability starts to become significantly more important. Just going for the highest DPS as a glass cannon isn’t necessarily the wisest move even in PvE.
Probably the biggest weakness I’ve seen for the Guardian has been the lack of really competent ranged DPS. That hurts in some boss fights and in WvWvW (unless you are rolling as support for a team, in which case you are golden, just might not get credit for kills as often as you would like). That isn’t near as much of a problem in sPvP since that has a lot more confined areas and shorter ranged fighting.
Figured I’d give you some perspective about high level Guardians. Personally I’m playing around with a Ranger since I want to see what it’s like playing with competent ranged attacks. (Also just an alt-a-hollic, so I’ll be busy a long time…)