In my Collected Company versions of Blue Devotion, I tend to run 2-3 counterspells because you need some counterspell interaction to buy time for your plan or to protect it
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Teysa Karlov creates double the value for your creatures dying, and commands this deck full of ways to sacrifice creatures with great triggers - especially those that generate creature tokens for Teysa to give vigilance and lifelink with her secondary ability
Theres even a built-in alternate casting cost for Emrakul with its madness cost of six colorless mana if you happen to discard it
One might argue that this is a "win more" card but given how much Marath wants you to have lots of mana, I think it's worth including