The same issue can be seen with Serra Ascendant: back then 20 life was always the starting life total and card text didn't account for alternative starting totals
Id expect Slash of Light to be good only in specific decks, as theres a real risk that this wont kill what you need it to
So, if your opponent deals you damage, they become monarch, and you cast another Azure Fleet Admiral, you get the monarch back
Despite its great power, it was overshadowed by many of the multicolored legendary Dragons that it shared a set with
Cards like Slither Blade can be a huge source of card advantage just by attacking every turn
A cardholder's worst nightmare is having an entire attack ready to commence, only to have an opponent play a card that steals energy