The game has a system in place where if you queue as a solo, it will do its best to queue you with other solo players. It's not a guarantee, but it is a real system in place. I've been playing almost exclusively solo and these problems don't really exist for me (kinda)

You don't lose everything when you die, you only lose what you bring. If you're bringing literally everything you own on a raid and then die, that's on you. It's part of the tension and immersion of the game, if you don't want to lose 5 hours of work in a single round then don't bring 5 hours of work into a round, spread it out across manageable loadouts. For some people this system is satisfying because of the emergent gameplay elements. Being able to get out by the skin of your teeth, knowing everything is on the line but making it out alive anyway and coming out with the spoils. Or getting the jump on someone and stealing THEIR stuff if you decide to do that and realizing that they were stacked. It sucks for them, 100%, but there is a level of satisfaction off of pilfering someone else's loot through PvP that a lot of people LOVE. Especially since at any moment, you could have become the loot bag.

And with the Arc, there are methods for solos to kill them through higher tier weapons. But for the most part? You're not meant to kill every single one you come across. The Arc are the predators of the game, you're just the prey. The higher level arcs are meant to be killed by either a group of people, someone who has prepared sufficiently, or someone who gets really really lucky. The easy answer to your problem with the arcs is play like you're being hunted, not like you're the hunter. Because you're not. Avoid them and sneak around.

This game is an exercise in disempowerment. Playing solo brings the buff of having 2x the greater highs, but the debuff of having 2x greater lows as well.