Paying four mana to do nothing else that turn is a pretty big cost in tempo
They just prevent damage, which, like gaining life, is rarely worth spending a card on
Overall itll play slower than the other eminence commanders, but access to blue means you have more control elements to take you into the late game
Tarkir: Dragonstorm has a whopping five precons this time around: Abzan Armor, Jeskai Striker, Sultai Arisen, Mardu Surge, and Temur Roar
One convenient piece of math that pops to mind is Modern Ad Nauseam
The Sauron starter deck, meanwhile, contains a range of dark creatures with powerful abilities but each relies on Lands being played, slowing down the pace of attack and requiring various blocking strategies to stay alive long enough for a killer hit