Saw similar deck on http://GatheringMagic.com a couple weeks back...
I'm thinking it might stand a good chance for Standard at Game Day...
Any thoughts as to how to make it more solid?

http://deckbox.org/sets/245964

Thoughts on its weaknesses against the common delver/jund huntmaster stuff (and how to improve)?

You might want to think about at least sideboarding some Haunted Guardians for use against quick aggro decks. Could really shut them down.
I would personally put a couple in the main, possibly in place of Doorkeepers.

You might also want to look at giving yourself more of a win condition than just mill and an easily killed big creature. Devil's Play might be good since you can easily generate the red mana, and with that you might want to put in a single mountain to search up when you happen to not have any Axebane Guardians.