As someone who hates Assasinate (I rarely put it in decks - hate the card, whether I use it or it's used against me), I love Called Shot, even if it can't kill commanders. Brilliantly designed card.
Called Shot was what some of us were pushing for during the Kickstarter. But after playing a while you do need Assassinate for the oh #$$#$ button. THat's also the reason why Calamity won't be removed.
I like that we have both Assassinate and Called Shot. Called Shot is good for when you would like to get rid of something...Assassinate is good for when you NEED to get rid of something.