One might argue that using a 4-piece set is the best idea; however, when it comes to niche sets like Noblesse Oblige, whose 2-piece set can boost overall burst damage. Things get a little interesting. I'd take the example of my Ningguang; I use 2-piece archaic petra to get a geo damage bonus, and 2-piece noblesse oblige to get a burst damage bonus. I like to use her as a burst damage dealer in some team compositions and switch back to other characters to complete the rotation successfully. I won't say the 2-piece 2-piece artifact set combination is bad. Still, you need to focus on your team composition to equip this combination with your characters. Most of the time, it's recommended to use a complete 4-piece set combination to take the most benefit from the overall set bonus and avoid ending up with odd artifact combinations. But, if you think a 2-piece 2-piece artifact set on a character can be good in specific team composition, you should go for it and equip it on the character.