Experience in vanilla dungeons is very different. If you are used to leveling up in dungeons on retail or something and your looking at 3-6 dungeons per level, its more like 5-10 times more dungeons needed. So like if questing at level 40 takes average 2-3 hours per level spamming dungeons at level 40 will be like 4-8 hours depending on alot of factors of course but proly closer to 8 hours. You will quickly find that questing is fastest way to level or grinding mobs aoe grinding mobs.
Keep in mind that records for fastest to level to 60 was like 3.9 days or there abouts. 960 hours 1.6 hours per level at an average
And that is hugely optimized not doing professions and doing no dungeons which isnt fun. Im expecting to take twice that like 6 or 7 days time played to reach max. I’ll have professions nearly done by then and I will have some dungeon gear.