if you wanted to just grind out level 4 for the healing spell by doing quests and such and farm equipment/shards etc would you be better off guesting in the level 50 no champion campaign that seems to be completely empty?
If you can solo resources and don't mind that taking you a long time, an empty campaign is probably easier. If you want to group up with other players and get AP from taking keeps and helping to kill other players, I'd recommend going to a more populated campaign where you will have an easier time joining up with a group.
No matter what your class is, grab a restro staff slot mutagen and go zerg surfing.
If you are magicka, yes. Grab a resto staff and heal. I prefer Healing Springs, but mutagen seems to give the best AP.
I've tried that on a stam character, and no. It didn't go well, and this is from someone who'd successfully done it on mag characters. What worked for me on a stam character was to grab a bow instead and tag every enemy I could reach so I got AP when they died.