Archer C3 is weaker actually. Scout C3 skill is actually the strongest autoattack replacer over here. It deals 500% damage on your auto split between 3 targets.
Flare shot deals quite high damage on immobile targets.
But yeah, it simply has too few useful skills.
Here is totally viable scout 3 build.
I won’t include rogue here since c1 rogue is bad. However if they add absolutely any additional skill to scout skill where I would be able to put obsolete skill points from cloacking it would become really good. This build has quite great AoE damage with 100% skill damage uptime, due to twin arrows and split arrows inbetween cannon barrages. Also you can combo Flare Shot with kneeling shot if you kneel right after launching kneel shot but before it hits and this way it will deal much more damage. That’s why it’s one of the few viable full DEX builds for archer. With all those crit rate buffs it will have HUGE crit chance - 80% base crit chance(from stats alone) against 0 crit resistance and slightly over 100% with full equipment and 1 level 7 cirt gem. This way flare will deal over 3k damage per hit with 0 attribute, and over 6k damage per hit with full attribute during 25 seconds(130k damage in total on staying taget). For sure snipe is better but still damage is already comparable. And if they add one more ability to scout skillset it will become really good.
Also it’s Split Arrow deals really good damage for quite a few SP. Overall it’s really worse then QS, Ranger, Wugushi C3 but better then Archer and Hunter C3. It’s also better then Falconer c2, due to Falconer c2 being rank 7. And it’s comparable to Rogue C3 and Fletcher C3(since they are also rank 7) and to Sapper C3. So it’s definitely not the worst choice (the worst is hunter, because it has only single target dps and it doesn’t affect bosses). Also it’s good for exploring.
Overall scout c1 is pretty great choice for some builds due to invisibility but scout c3 loses to scout c1 rogue c2 musketeer or scout c1 ranger c3 cannoneer.