I know this is an old post from June of 2021, but screw it, I'm gonna reply anyway.
The Guardian is an archetype that is capable dealing damage while having the ability to offer heavy support to your teammates and even to yourself. Their inherent ability known as Resolve grants them the ability to acquire Status Protection and Absorption after defeating an enemy. This inherent ability stacks up to three times, and can affect nearby teammates.
Their survivability is a bit better than a Blaster, Corruptor, or Dominator thanks to their Composition power sets granting them defense abilities. While their survivability doesn't measure up to the Brute and Tanker archetypes, their overall damage output and support capabilities are perfectly balanced, making the Guardian an all-purpose character in a sense.
However, the Guardian itself can be a massive endurance hog if you don't plan out your build well. It's best to give yourself Endurance Reduction enhancements for the abilities you get that require you to use a lot of endurance. Even if it won't help with the endurance problem much, those enhancements will make a difference, especially the IOs that you may want to craft that relies on recovery and endurance reduction.
Overall, the Guardian is a solid archetype that delivers everything that you can possibly need for bringing villains to justice or gutting heroes like fish, but they don't hold a candle compared to the Blaster or Stalker in my honest opinion.
That is all. My honest opinion on the Guardian archetype.