Convoke ( Your creatures can help cast this spell
You can take out any problem card stopping you going off, winning or just living regardless of its size or card type and you can do so for relatively little mana compared to the appropriate hard removal spell for that thing
Meanwhile, Grists +1 ability gets better when you mill insects like the Cultivator
Cards that consistently draw cards on our opponents' turns, like Ephara, God of the Polis, allow us easy opportunities to miracle Tide on an opponents' turn
The mill will take some cards away from them (unless theyre a graveyard deck, obviously) and give us juicy choices
I dont know if The Scarab God currently has a home, but it is a powerful card that may be just the tool Dimir needs to find a fully fleshed out deck