I went over some other character tags, including voldemort and darth-vader, and it seems like they take a different view of how to structure the tag wiki, tense-wise.
The major antagonist of the Harry Potter series of books by JK Rowling, a powerful evil wizard who seeks to cheat death and rule the world
The major antagonist of the Harry Potter series of books by JK Rowling, later adapted to film. A greatly feared dark wizard, he seeks to dominate both the magical and non-magical societies in Britain and maybe further. He is completely amoral and unable to understand loyalty (vs intimidation), friendship, or (most importantly) love.
What we see here is a description that tries to address the character in general terms, not in any specific point along the fictional timeline. You don't need to address his actions in the books, but look at it as an encyclopedia entry about him, either in-universe or out: he is the main antagonist in the novels, since we're not before or after reading them, he just is. He is completely amoral, when describing him, not at any point in time.
And for Vader:
Darth Vader is the primary antagonist in the original Star Wars films. Wearing a black armoured life-support suit, he features in all three original films. As a master of the dark side of the Force, Vader became the scourge of the Jedi, leading the Great Jedi Purge. [..]
Darth Vader is the primary antagonist in the original Star Wars films. After a battle with his former master he was badly damaged by lava; Vader is seen in a black, armoured life-support suit. [..]
This gets a bit more complicated. It seems the tag wiki here is written from a point in time of when the character is first introduced, in Episode IV - he fell into lava and became the scourge of the Jedi before the first point in the narrative, so it's not an occurrence in the plot (though it would later be, in the prequels), but a static description of the character as characterized.
Don't Kill Dumbledore
Judging by these, I think that a better update to Dumbledore's tag wiki would be along the lines of:
Albus Dumbledore, a powerful wizard, is the headmaster of Hogwarts School of Witchcraft and Wizardry throughout most of the Harry Potter novels, and a major character in the plot.
Don't change "is a major character" to "was a major character", because he still is a major character, in the sense that the books still exist and he's still a major character in them. Instead of "he is a powerful wizard", go for "he is one of the most powerful wizards in the Harry Potter universe", which is true because it describes his position in the story and universe, not in a given point in time.
And remember, there's no need for the tag wiki to be fully detailed, or even up to date with everything that's happened, just the snapshot of the character that encapsulates them. Would you say it would be wrong to say that "Harry Potter is a student at the Hogwarts School of Witchcraft and Wizardry" because the final scene skips years ahead, placing the "last known point" of the plot when he is no longer a student? I don't think so. His being a student is his essence, in the novels, just like Dumbledore's importance lies in his being the headmaster.