As Kaivax points out in a post last night on the official forums, monster health has been increased in the Beta of Dragonflight so that the duration of the fights is closer to what the developers want.
The team expects the average player who goes through the leveling experience with one of the predefined characters to face a single enemy for one or two spell rotations. There are a large number of players of different skill levels and the developers expect players to have a different experience as a result of these changes.
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