I was thinking more quick to make hotkeys for instant use, than having to go into your menu every time you wanted to set a new hotkey. Even a dedicated button for a 'repeat last action' would be super nice quality of life feature.
The way I described it in my root post feels like the most intuitive way to use hotkeys for an ever-changing environment. Passing out buffs to your group - hotkey your buff spell for a quick 5 casts. chance encounter with a monster weak to one element while you're in an area populated by other things, quick hotkey to a better spell for just that moment. PvE turned into PvP, hotkey to a spellbook page instead of having to frantically scroll to it.