From a roleplaying background it makes totally sense, as it's definetly not a good action to consume souls and not just a free recource laying around. So to improve background it certainly worked to show the bad sides that sourceres have.
Unfortunately it also deleted 1/3 of all avaible skills for my characters so thumbs down from me for that decision. Either let only the real OP, vile skills use source and the middle powered ones just have higher slot/AP cost, or just stop using source as a secondary currency for spells at all.
The current way is just boredom for any "good player" and their 5 basic skills and nothing advanced.
