To recur a permanent three mana value or less when it enters and when it attacks makes it possible to keep recurring things you sacrifice or block with
When x happens, draw a card seems to make up a large portion of many recent staples, and more and more legendary creatures with a built in card draw engine get printed and played, so having your opponents discard down to 6 instead of 7 can be a great way to slow down their game plan
They just revealed several new Planeswalkers, revealing the full cards for Teferi and Liliana, and teasing that Chandra (the fiery red Planeswalker) and Garruk (without his curse, meaning he will likely be mono-green again, and not a Green-Black Planeswalker)
While it takes Ral a few turns to get there, cards that proliferate can speed up the process
Decision Point: Naming a Creature Type Cavern of Souls and Unclaimed Territory are the glue that hold the Humans manabase together
That drove my design of this one