You are able to take quests 10 levels higher yes, and you’ll also take more damage while doing so.
You can CC the spion archers (as my Sorcerer did using Sleep), you can travel in a party.
Overwhelming majority of classes have CC and in some cases you can simple avoid them (Fade for instance of Cleric).
There is a Ton of in-game solutions even when underleveled to do quests in that area.
Spion archers only do credible damage because of Spiral Arrow, outside of that the damage is nothing special. Again you see Spion archers as early as your 20’s back in the Klaipedia side of the game, and they use Spiral arrow as well and it can take out 60%+ of your health even back then. However again, Crowd Control, defense skills, partying, etc allow you to get over this.
In the early game spion archers have next to no health so you can basically kill them before they do damage. Here while some classes can still manage a 1 or 2 shot @ 225, you ideally just want to use the assortment of tools that are available in the game to mitigate or prevent damage. The most simplistic and general of them is to up your defense with a Shield and Aspersion. Getting 600 Def in this case is fairly easy so then what is hitting you is the increase from the level penalty, which IIRC is 10% per level starting from level 5. That should be 60% more attack which is about what around 360.
Won’t be much of a problem unless they crit.
A cleric can just heal themself after eating 1 spiral arrow, if they dont already Safety Zone or fade it, or dodge it due to Aukuras.
Wizards
Sleep 5/10/15. Hell even Lethargy reduces the amount of defense they need to reduce damage to 1. There is of course Cryomancer’s crowd control, or Hell Pillar (though its a long CD) as a pyro.
Swordsman - Can Block the Spiral arrow (Peltastas will also get a defense boost for doing so), Or they can just eat it given Swordsman have 1) Higher base health than everyone else 2) Higher base defense than everyone else.
and follow up with Crowd Control.
Archer’s can also aim to CC. They can lure with Pavise if QS, use a pet to course/retrieve/Rushdog if a hunter, Crank up the evasion with Swiftstep and maybe plant an Aukuras skill scroll if they want to rely on RNG. Attempt CC with things like Flu Flu, Stone shot, etc.
Though I still just recommend Plate + Shield + Aspersion, handles it easily and there is a statue of valkarine their so you can get your aspersion whenever you have to travel in that map.
Of course travelling in a party you suddenly have other people making life even easier, and killing them before they attack can be a real possibility.