What are his best lows in Staff?
1f1 xx GB from mid to max range is really good. Although if you spam 1f2 from max range like 2 or 3 times you'll be super close to them, but by that time they're usually so trained on blocking the overhead that a point blank 1f1 will take them by surprise, follow up with whatever you'd like.
edit: So I've been messing around in the lab today trying to address one very serious gripe I have with Dick. His crossups. They're so hard to land successfully, j3 knocks down so getting a nice damaging combo is hard due to lack of air juggles and his J2 hitbox is so wonky it's hard to find that sweetspot you need to use it. I think his jump ins give a significant enough damage boost to his combos that they warrant some bit of exploration for applicable use. These set ups are for landing j2 since it's a better combo starter, but you can sub in a j3 if you really want that knockdown. Here's what I've got so far, this is a work in progress:
on hit - d12 xx 4 db3 xx 4 jump forward twice j2 on second jump.
This set up puts you into perfect range to hit any character with either a cross up j2 or a non-cross up if you hit j2 early in the second jump on a bigger character (grundy, dooms, lex) I'm not sure if anyone else knew already but if you press 4 during the db3 nightwing will do a different looking stance change back to escrima stance. It's important that you hit 4 DURING the spinning staff part of the special and not during the splat or it will not work.
on hit or block - d12 forward jump j2
This one is super great since d12 is pretty + on block you're ok to just throw it out if you're fishing. On block you can jump over and get an easy cross up if they're stand blocking, but if they're crouching you'll have to dealy your j2 just a little tiny bit to smack they're hitbox. If you actually manage to HIT with the crouching d12 then the hit stun will actually prevent the opponent from crouch blocking in time leading to a super easy standing cross up. Give them your hypest combo!