First off, i think this bonus should only be applied upon having one character at that level point already, that way you aren’t just speed running bot accounts after they get banned.
Secondly, it’d be nice if you applied that buff a few weeks before the phase ends so those of us who are hitting gear cap and are getting bored will have something to do to fill the time. The ideal time to level alts is when there isn’t anything better to do, not when a bunch of new content is dropping.
Just because you don’t like the answer it doesn’t mean it isn’t the answer. Every iteration of classic wow has led to floods of forum posts that more or less say “is it too late to join in?”, and the xp buff and the phased leveling is an attempt to address that.
You don’t have to like it, but you can’t pretend there is no reason for it.
50% base and then 10% more for each 25 you already have. having done it all 5 times over again already id like to just ding the next char and start gearing it already. done that quest 5 times over+ some over the year lets make it quicker this time.