Because any point after 200 cost 3 attribute points, fill STR to 150 and you will have 3STR for every DEX over 200. Bow and dagger scale with DEX and little with STR, so you don't lose as much punch, though craftable 2h swords scale with STR/DEX, so you deal monster 2h damage for an archer
81 CON and light armor is a glasscannon so use 2H very wisely. Why use 2H and not dagger if you have a skill to match? Because reach, and shield on back.
Onto the last quirk of this build, 15pts into medic tree, you can revive friendlies for FULL hp, while the shield on the back will protect you from enemy archer interrupt if you position yourself nicely. Don't do this on the front line, you'll die, but use your stamina/ammo downtime to get friendlies back into action
It used to have more sense before free bandage changes and max revive cap, but is still powerful