turns out its about half that if you do the 6 month at a time thing, but i see your point. though the casting time makes a little bit of sense (takes time to conjure the spell, especially the powerful ones) and it allows another option for them to fiddle with for game balance (because if magi were as powerful as they should be in games, it would not be fun for all non magi)
as for my personal least favorite game mechanic, never really liked quick time events, but they can be useful (like in infamous where to heal or leech people you had to do a very minor quick time event, like a double check to make sure you didn't accidentally do the karmatic opposite thing).
also hate time limits most of the time (again, sometimes they make sense)dislike invisible barriers (if i shouldn't go somewhere, lay a minefield or put a wall/fence/wall of men with guns on hair triggers and even shorter tempers) and it really bugs me with a noticeable lack of voice acting in single player games. just seems lazy.
and finally, dipshit Allied AI, because it seems the enemies sucked all of their intelligence and use it to absolutely destroy you, and your allies cant remember how to do much more than shuffle forward and pull the trigger at anything which resembles a mobile organism. becomes especially irksome on higher difficulties, when it would be nice if your allies could draw fire for more than a second, cover a flank, actually do some damage (in rts games and fps games. rpg games seem to not suffer from this problem as much)