I also prefer to us Kleptomancy when playing Nasus, simply because it is the strongest rune for him as of patch 8.4 despite the debuffs. However, it comes at a risk: you give up on laning phase (not an issue for Nasus, but...) and sometimes getting 3 runes instead of 2 from Resolve can mean a lot. Also, the items you get are random, so you can't exactly rely on them, making Grasp a bit more "reliable".