Dean was extremely thankful to Harry's mum for offering him a job. Though now that he's working for her, he should probably start thinking of her as Lily, not "Harry's mum." In any event, he's not the best at potions, but he's tall and can thus reach the high shelves better than anyone else can, and he's got good penmanship for labeling potion vials.

His customer service attitude could probably be better, but then he can't help but be shocked at some of Lily's pureblood clients. He does his best not to say anything, though. He just keeps his head down and lets Lily handle the customers who were Death Eaters in his own timeline.