I know that this works, but I consider it a bug. After all, what reason should there be that you become visible when attacking a foe the normal way, but remain unseen when swinging at several enemies close by? You can also cast Elemental Strikes at enemies from afar after becoming invisible, and they won't react, but I consider that a bug as well. Making use of it would make me feel I've cheated my way to victory.
FFS is a great spell, but it's my impression that a longer duration (or a lower mana consumption) isn't worth extra skill points if you compare it to the proposed effect increase of a fireball. An increase in the quality of the spell might be necessary, so at level 1 people might have a certain chance of still noticing you because they can hear you or your veil is imperfect. Whether additional effects for Wizard's Sight would be worth more skill points is hard to tell. My point was that if Larian finds it hard to balance spells and to increase certain effects, it would be better to have lower maximum levels for some spells than to have extra levels that aren't really worth the skill points.
And mine was that a spell can often be what you make of it <img src="/ubbthreads/images/graemlins/smile.gif" alt="" /> Sometimes a spell that seems to have a very limited use can turn out to be incredibly useful, after all, if just applied in the right way <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />