Note 2: There might be some 2/1s, you can generate for B in other ways (like Sarcomancy, which is an enchantment for B that produces a 2/2), but I didnt bother to look for them
Every Warren activation does 6 damage to the opponent
Recast Chun-Li and the threat is immediately back online
This pushes most typal decks in the same direction, and the design team was interested in finding designs that were good enough to warrant adding cards that weren't creatures of that type
Even with the downside, the benefit you get from information and making them discard a key spell is worth the life loss, and control/combo decks hate to see a turn-1 Thoughtseize
If these games go really slow, then some of these might be good at breaking those stalled boards, especially this Crystal