The current mob and object respawn time in Northrend especially in entry level areas is too high.
In Outland interactable quest objects respawn instantly. They have 2-5 minute respawn time in Northrend.
Even the most basic mobs have 5 minute respawn meaning every single quest turns into 20+ minutes long wait.
Just in last 2 hours 80% of my questing time was spent waiting for mobs to respawn.
edit: this was regarding Frostmourne realm

