Nightwing is really two different characters with a "tag team" trait. One character (staff stance) is great against grapplers and rushdown, and has moderate tools against zoners, but extremely weak against flying characters. The other character (escrima stance) may be better against flyers, but is low tier at best.
If for some ungodly reason NRS decides to nerf staff stance, they need to buff escrima stance. Perhaps an "up" option for MB Wingdings?
Staff isn't that great against grundy though. Grundy 2 has roughly the same range as the staff and leads to a 50% combo on hit. grundy dash beats ground pound. He has a lot of unthrowable frames so walking corpse doesn't always work but WCC works wonders.