Cloud of Bewilderment is a very good spell, (as an aside it is even more Powerful in Neverwinter Nights 2 as it gives the Stunned condition rather than Nauseated).
For an Adventure Path I would say do not sweat it, there will be plenty of other combats.
I foresee a Sculpted Cloud of Bewilderment & Sculpted Black Tentacles in your future though....
Being limited to just a move action in an everything but the kitchen sink game, is not a debilitating as in Core. There are many feats, manuevers, Spells that are Swift, Move, or Immediate actions. A general rule of advice is if your players are tricked out, you need to trick out the climactic battles as well....especially for spell casters.
Also clearly the spell will not work on undead. Given that it is a static spell that effects anyone that enters the cloud, you can also have monsters use it to great benefit, (in my own game, I have had a Large Monk throw the PCs into the effect).
I do not have my book handy, but if the spell is actually a cloud and dispersible, Gust of Wind will get rid of it. I am assuming for your own party everyone goes ranged weapons when the spell is cast? Otherwise, beyond obviously taking a move action to get away, I would try to move the monster to a position where the melee PCs also have to risk being effected by the spell. In the case of the Grell, would the grappled PC also not have been effected? Nauseated + Nauseated + Grapple would equal Dropped PC in my book.
Sculpt spell as a feat seems too powerful here.....I might just be remembering the Archmage power, but I thought Sculpt Spell allowed you to add little breaks in a spell, (allowing you to cast a fireball w/out burning the fighter) and change a cylinder to a line etc.