MMR

1. Общност
2. Feature Requests and General Site Feedback
3. More exercises for advanced math (multivariate calc, linear algebra etc.)

You are right. The advanced math sections are definitely lacking in exercises. I hope that this will soon be prioritized. 

1. Общност
2. Feature Requests and General Site Feedback
3. More exercises for advanced math (multivariate calc, linear algebra etc.)

How well does this fit with the need you describe?   https://www.khanacademy.org/math/multivariable-calculus