There's no way you live through 20 people focusing you for any more than 5 seconds (outside of shit like Earth Armour that makes you invincible, but for what... 3 seconds?), sorry. Like I said, you can make it work, but jumping head first in to huge groups is gonna get you killed unless you know what you're doing (IE when it's safe to go in, etc, which the way I see it isn't jumping in head first). I've only ever seen you in WvW once so I don't really know how much experience you have there, but if you've ever fought inside Stonemist Castle you'd know the kind of clusterfucks I'm talking about. Fighting against large zerg groups = good fucking luck meleeing anything but stragglers outside of the pack. And yeah, ranged options on Guardian are far worse than GS, Staff is trash (Scepter is the ranged DPS weapon, Staff is support with minor damage) comparatively but it does the job for stuff like defending against sieges. Gates get non-stop spammed with aoes, if you happen to jump down and try to melee those hitting the gate... yeah, you're just gonna insta-die. You can head for the ranged people and down a few of them, but whilst you can burst a couple down you'll get immediately focused and killed before you can finish any of them, so they'll just rally/rez. Exception being if you can manage to convince other people defending to jump down with you, but good luck with that part.
As for farming karma, running with the zerg group in WvW is usually a great way to get karma, used to be able to get tons even in small group(s) thanks to caravans, but the rewards for those are still disabled so your best bet is defending or attacking locations. If the zerg is being stupid and just fighting in one spot nowhere near a location, don't waste your time since you won't get any karma for that. You can take over supply camps with just a handful of people, as well as the monster camps (Dredge, Ogres or the Quaggans), so those are good at times like those.
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