I think it all depends on gear.

Humans is str/dex/vit. You need to go hybrid, unless you have enough gear adding dex. Guardian gives accuracy boost, splitter (normal attacks to aoe) and your ulti I believe gives you hp leech every 45 seconds for x-seconds. So farming etc is easier BUT your defense is much lower compared to a defender (who has also lower attack and less aoe dmg). These two are rather balanced so to say and it's purely up to preference and gear. I haven't met many guardians that can solo much yet..

Dhan = predator.