You might try dropping the nullrods, and adding more shaman and another cannonist.
Null Rod aggro without Null Rods seems to be increasingly popular, but I don't know if it works here. You're right about needing more one drops though. Since aggro Workshop and Tarm/Fishy kind of decks are the biggest problem right now, I like Canonist staying at 3.
Personally I don't think you need jothun grunt for yardhate when you have so many better options for GY hate in black, so maybe you can run grim lavamancer instead. It also improves your fish matchup
I kind of want a 2nd Grunt just to slow down Tarm and outsize other Fishy creatures or trade with Lodestone.
So what's the metagame you're preparing for? What decks do you want to be good against?
Such information would help others give you more constructive feedback.
I don't really have a local Vintage metagame, so I'm just trying to prepare for the generally most played stuff.
Playing Grim Lavamancer might enhance the Fish matchup.
I'm having trouble fitting him, and I'd especially be wary of adding him if I fit a second Jotun Grunt.
Hearth kami vs shaman: Which has been performing better? If you're lucky, the answer is shaman and you can smooth your curve and play the arguably more powerful card. Kataki is another more powerful alternative and if you play against shops it should definitely trump kami in the sideboard. Duergar hedge-mage is a very greedy card, but your manabase should be able to support it. Maybe it warrants a slot in the main and one more in the side?
Grunt hoses goyf and welder and is your best clock. You could play 3 of them. Overseer is missing the point a little bit: You play him for his size and because he trumps goyf. Yardhate is just icing on the cake. Lavamancer is good though, and the two are not mutually exclusive.
Are the 3 REBs in the main really necessary? If you are so impressed with hide/seek, you might want to play one more in the main. Lightning bolt may be an alternative to REB. What are the blue problem cards in your meta?
Kami has been so much better than Shaman most of the time, even when I draw Shaman first turn. I still went ahead and upped the Shaman count to make sure I have something to do on the first turn of every game. I'll try out Kataki in the sideboard, I used to like him a lot. Hedge-mage is very interesting...
I'd be wary of a third Grunt, but I really want to try fitting a second one in. Would it be weird to put him in the board?
The REB slots were always in flux, and I've tried Bolt in that slot before. Bolt is neat in that it will kill Jace most of the time as efficiently as REB does, though the REBs let you do your normal early disruption and then use REBs to stop any draw spells while you lean on them with some beats and strip their final answers with Hide/Seek. Bolt would help with the creature problem a lot though...
Current list:
2 Shaman
4 Confidant
3 Tidehollow
3 Canonist
2 Hearth Kami
2 Mindcensor
1 Grunt
3 Thoughtseize
1 Duress
2 STP
1 Diabolic Edict
2 Hide/Seek
1 Demonic
1 Vampiric
2 Pyroblast
1 REB
1 Extirpate
3 Null Rod
1 Lotus
1 Pearl
1 Ruby
1 Jet
4 Wasteland
1 Strip Mine
1 Plains
2 Swamp
1 Mountain
2 Badlands
2 Scrubland
3 Plateau
3 Arid Mesa
2 Marsh Flats
SB: 2 Hide/Seek, 3 Yixlid Jailer, 2 Ravenous Trap, 1 Jitte, 2 Kataki, 1 Darkblast, 3 Lightning Helix (testing)