Putting people on too many projects (6 projects) is bad because when it comes to reviewing your work (let's say 30 x 200 lines of code), they will spend 5 minutes on it, 10 tops, give a shitty, lazy review and then they get back to their projects.

This is just pure mismanagement. You're stressing your employees to get everything done, the 'quality' is then spread so thin everything turns to shit.