Sprout feedback/Question.

[Rilifane]

It's normal.
Even without doing any extra content (like roulettes) you will continue to be overleveled. Most people are 80 way before reaching the end of ShB. They buffed the experience more than once iirc. Before the first buff, there was gap at around 36-38 and 48-50 but now you'll likely be 54/55 by the time you reach HW.
I know it feels wrong and as if you you are "behind" in MSQ but it does slow down a little bit. If you don't want to feel like you're constantly too far ahead of the MSQ, a solution many players use is leveling more than one class at once. Since you're already 28+ with quests and can't unlock a class starting at 30 unless you reached HW, you'd have to level one from 1. It's fairly easy to catch up though.
Or you wait until 50 and go for RDM/ SAM if that tickles your fancy.

[LianaThorne]

It's normal.
Even without doing any extra content (like roulettes) you will continue to be overleveled. Most people are 80 way before reaching the end of ShB. They buffed the experience more than once iirc. Before the first buff, there was gap at around 36-38 and 48-50 but now you'll likely be 54/55 by the time you reach HW.
I know it feels wrong and as if you you are "behind" in MSQ but it does slow down a little bit. If you don't want to feel like you're constantly too far ahead of the MSQ, a solution many players use is leveling more than one class at once. Since you're already 28+ with quests and can't unlock a class starting at 30 unless you reached HW, you'd have to level one from 1. It's fairly easy to catch up though.
Or you wait until 50 and go for RDM/ SAM if that tickles your fancy.

+1 to this. I started with DRG, maxed to 80 and then switched to SMN for Shadowbringers after leveling it to 70-71.