So I decided to level my necro doing the bread quest and I'm happy to report 16-24 went by fairly quickly. I began roughly 71% into Lv16 and I misplaced the data for that level but below is a screen grab of the google doc I updated as I was running back and forth.
151 turn-ins/quest runs were tallied, with I'd guess an extra 4-5 not recorded from Lv16 and an addition 4 runs to give myself a bit of a buffer after I hit 24. Each run took 5min (counting load times), so in total this took around 13.33 hours though spread out over a week.
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Recorded my exp bar after each turn-in, and had some very basic formulas counting how many per level, a running total, difference in exp bar after each, and average % difference.
Spoilered here is a gif of one of the runs, to get a feel for what that joyous adventure was like just watch this 160 times.