Is Razormane Masticore just not good? I posted about it earlier, and I'll admit I have not tested, but on paper it seems so good for the meta. Providing a discard outlet outside of Bazaar, and being able to nuke opposing Welders, Wizards, Levolds/Dr Shamans, and just being a beat stick seems very strong on paper.
Tasigur might be a nice inclusion as a 1 of creature to do infinite things with as well. I like it 
Why no Channel or Trinisphere? Being able to channel turn one off an ESG and poop out your entire hand seems amazingly great in this list.
Edit: notice your lack of green sources. Noted.
@myk I tried out your first list and really liked it. I tried something a little different, not much, but was interesting. I replace 1 Grove for the 4th Sanctuary, and played 2 Regrowth instead of Ramunup and Exploration. Sanctuary is so powerful already with 4 Treasure Hunts, the blue restricted draw, and Walk, but Regrowth with it was very strong for getting back a Crucible or Fastbond previously countered/vigored/discarded. Regrowthing a Treasure Hunt leads to busted turns as well obviously. I love the list, test out the regrowths and 4th Mystic sanctuary, it's really good.
Treasure Hunt and Fastbond with this land seems very, very, very strong. Casting multiple Treasure Hunts could literally lead you to drawing your entire "lands" deck in one turn. Just a thought I been churning with, no decklists yet, but an idea to throw out there for you guys/gals.
You can discard this to Foil, return it with Crucible, get your Foil back on top, Gush, and do it again. Talk about broken.
Have people not considered this for Hermit Druid decks? With the new Mulligan rule and this, getting a turn one Hermit (especially with 4-8 Guides) seems very strong.
If welder takes off now that derpsteps gone, I could see some neat steal your welder, I win scenerios happen, but outside of that I don't think this is viable. @Mike-Noble shows how much I follow new cards and what format they are allowed in 
"But I don't understand his Hogaak only cost 2, why can't I steal it?" - most common question of standard in 2019