Its reliable and efficient, but not versatile, if youre a super fast combo deck, this jumps up several ranks, but even for slower blue decks, this tends to make the cut for me
First, it could be a huge mana ramp for the casting player , as you'll be able to attack the turn it comes into play and then tap all your land for double mana at the cost of that much damage
Similarly, if an effect would cause you to exchange life totals with another player, the exchange won't happen, and neither player's life total will change
Lifeline is a pricey Reserved List card that is absurdly powerful and gives you a full free refund for your sacrifice
Having debuted in a Commander precon, she has never been Constructed-legal outside of Legacy and Vintage formats where aura-centric strategies rarely flourish and arent looking for help from a three-color four-drop in any case
Even if it does eat a removal spell a few turns later, its often too late