A 3-mana 3/3 with Vigilance is a great place to start, and doing dungeon stuff every time he ETBs OR Attacks is incredibly good, and that would be true even if he didnt also give you a massive bonus for completing the dungeon
From my understanding, the spell just needs to be cast from you hand but doesn't actually need to resolve, so while you can't just Fork the spell, you could Remand your Approach of the Second Sun and then recast it to win
6 Lucas, the Sharpshooter A 1/3 human that costs one blue and one red, Lucas the Sharpshooter has Friends Forever and can tap and sacrifice an artifact to deal one damage to a creature, then goad it
We will likely still tweak some things, but other things may naturally fall into place as more people try out and discuss the system
The front half gives you consistent card draw with its triggered ability that rewards spellslinging, while The Great Synthesiss first chapter provides a huge burst of card advantage
In terms of sheer lore (yes, this is something that I absolutely care about, possibly more than I should), I think the deck works perfectly