I agree. The teacher feels like an afterthought. I didn't think the pacing was slow...rather, the character-specific scenes were just too few to actually create any real buildup between the protagonist and the girls. They could have easily trim a number of general scenarios not related to the game since they didn't seem to affect the storyline or the girls' scenarios.
Rei's and Kozue's H-scenes were nicely drawn, especially under the Sakura tree. The others were so-so. Which makes it all so disappointing because the potential here is untapped.