Good catch - this was real and it was ours. Holding the attack key swung exactly ONCE: we required you to release and re-press between swings. v83 has no such rule (the client polls is_key_down(ATTACK) every frame and the only gate is 'not already attacking'; MapleStoryUnity's action scripts poll GetKey the same way). So your actual damage output was capped by how fast you could mash the key, which reads exactly as 'the enemy takes a second and a half to die'. Attacks now repeat while the key is held.

(On the dev branch - it will be in the next published build, not v32.)