The game has infinite source pool on Act 1 2 and 3 once you find the location of the source fountain, and all of them can accessed really early.
When the game gives you infinite source, you really can't balance them around not using source spell anymore. At this point, the cost are just there so you can't use MEteor Shower AND hail storm in the same battle on the same char without drinking source potion or being in a certain fight.
"Infinite Source" is a bit strong. If you run out of source/source potions, you cast that spell and then your mage is useless for the rest of the fight because the physical damage dealers will run circles around him.
The tediousness of always draining corpses, making potions, or looking for fountains ( to even be somewhat efficient once your mage got his buffs out) doesn't make it better.
