I do not think that a shorter casting time would make that much of a diff.
"ooh, I can get off more
spells faster just to have a mob turn on me, wow! that is so much better
then a magician". That
is just my take on it. I would rather have concentration allow for more mana
efficent casting, which
can be done by reducing the ammount of mana needed, or by upping the damage
done.