The effect of "Ceruli" from the opponent's field will allow a player to activate "Triple Tactics Talent" and "Triple Tactics Thrust"
Esper Control is probably the third most-popular deck in the format right now, but is Chromium likely to be more of a mirror-breaker in the sideboard, or a versatile maindeck threat
Ravnica: City of Guilds was cohesive, and it wasn't all about humans or the city itself, but it heavily featured all kinds of creatures that could inhabit the plane
More importantly, it does some really fun, unique things
Basically, the deck feels unbalanced, and if players know your strategy is basically to go all in on creatures, they're going to be far more aware of your combos and keen to stop them
They would escape, causing the shift in the block's mechanics