Greenstone.Walker
Adventurer
Because then no Rogue would ever take any other weapon. If a weapon is "no class would ever use anything other than this", that's a good symptom that it is horribly overpowered.I don't understand why you can't just make the spear a Finesse weapon and eligible for Polearm Master and call it a day.
Imagine a Rogue running towards a foe, stopping 10 feet away, stabbing them including stealth attack damage, then running away, all without ever risking any attack of opportunity. If the foe follows them, the Rogue attacks the foe from 10 feet away, possibly with steal attack damage again.
From a realism aspect (yes, I know

There are no versatile, two-handed or heavy weapons with finesse in the game. I believe that is deliberate on the part of the designers.
Also, to answer the original question in this thread, why do you say Nuada is a DEX fighter? From what I remember of the movie, he shows a lot of strength in his workout and fight.