Why does the moose boss have 3000 health even though it's in the recommended lever 1 area?

There are recommended level for all bosses in WC. These bosses are meant to be defeated as a team unless you're an individual with high level creatures. For the moose boss, the minimum recommended level is 20, that is, if you try to defeat it as a team. Grind until the levels of 60-80 and decently elixir boost your creature if you want to defeat it alone.