Writing here just to stress this point. I'm in the same boat as OP. Decided on Wed last week, that I wanted to level a new toon, but refuse to do it during double XP. Waiting since then for the devs to remove the bonus from the game. The problem is simply that you have no chance of gathering enough crests during double xp times, so you end up not buying any renown level gear in order to be able to afford at least Conq or you buy level gear and end up with Annihilator.
The entire situation gets even worse when you take into account that rested-XP and the double-XP from the event stack multiplicatively. If you can only play during the evening and maybe not even each day of the week you are basically drowning in 4x XP.
Would love to see the rested-XP mechanic get a rework as it has become detrimental at this point. I'd rather have a rested renown mechanic. If you make it cap after like two days it would also encourage players to play more consistently in order to maximise their renown gains.