While I do like the general idea of the monster specific adventure, it is a bit sparse in the execution. Some things are just named once and then dropped to never again appear, like the thieve's guild. The other adventuring party could be massively more fleshed out as far as actual interaction goes, as example putting two into the trap and only the twins onto the shelf would allow the next fight to point some save or suck abilities at them. Same goes for the "potentially rescued mage", who wants to be left behind even if he has like thrice the level of the party. Also his utility spells (plus his knowledge) are sorely needed in a few cases. Also I would expect him to unload dirt on his colleague if he gets rescued, which should be probably prepared in some way.

To fix the thieves guild, I would also not let the guy that plants the bomb magically vanish, but let him be caught and interrogated, so involvement of some arcane client can be established. Also the bomb sucks, as it either means the party is dead or they will stay one or two additional days in town, having it tie into the story give it at least a tiny bit of reason.