Domination vs Dueling
Clones overwrite other clones before they overwrite phantasms. Only if you have 3 phantasms out will a clone overwrite a phantasm.
20/20 is generally better than 10/30 because you will struggle to find a better 3rd trait in the duelist line than the vuln on daze minor in the domination tree, which provides a huge amount of vulnerability for your group’s dps.