I can understand the viewpoint of it being a bit of a hassle though if you're the kind of person who would seriously go back to town after every single battle in order to use the skills every single battle...
Yea in Baldur's Gate this was solved by having you have to rest to restore spells and having a % chance of enemy encounters during the night.
Even that system had it's flaws but I feel it's a better system then just forcing players to waste time using fast travel to and from source fountains if they want to use Source abilities regularly.
If you used Baldur's Gate's system combined with a system in place where certain quests had timers tied to how many days it takes you could add urgency to only resting when absolutely necessary, just like in most DND campaigns.
Though I still think high AP costs tied with long cooldowns and high combat ability score requirements could make abilties powerful, but not constantly spammed. Source as a resource just seems entirely pointless.
