Burn is really a pretty simple event, allowing Maldaria to do some cleanup faster than the opponent expects, but it is also a “trick” event, since it’s playable in the move phase, so it can allow the Phoenix Elves to attack targets the opponent doesn’t expect, or get into spots the opponent didn’t expect (or want) you to get in. For example, you can use this to take the front of a gate that has a 2 life unit in that spot.
Despite its short range, Burn is a very powerful and versatile event, because 2 damage on a whim for a single card is very efficient, and so it is generally worth it to just throw it on most units that are not super life-efficient, so at worst it’s a very efficient event, and at best it can be a swingy trick that wins the game.