In the sphere of software engineering, particularly within the domain of C++, designing reusable classes is a coveted objective. Reusability fosters efficiency, consistency, and maintainability. However, achieving this in the intricate landscape of C++ is not without its challenges. The following is a comprehensive examination of the main obstacles that developers confront when designing reusable classes in C++:

1. Complexity of Inheritance:
   • Deep Inheritance Hierarchies: While inheritance promotes code reuse, a deeply nested hierarchy can lead to a loss of clarity and increased maintenance challenges.
   • Multiple Inheritance: C++ supports multiple inheritance, but it can introduce ambiguities, especially when two base classes have member functions with identical signatures.
2. Template Challenges:
   • Compilation Errors: C++ templates, though powerful, can produce verbose and convoluted compilation errors, making them difficult to debug.
   • Code Bloat: Overuse or inappropriate use of templates can lead to code duplication in the compiled binary, increasing its size.
3. Memory Management:
   • Ownership Ambiguities: In a reusable class, it can be challenging to determine who owns an object and is responsible for its deallocation, leading to memory leaks or double deletions.
   • Shallow vs. Deep Copy: Creating reusable classes requires careful consideration of copying semantics. Mismanagement can lead to unintentional sharing or excessive copying of data.
4. Lack of Reflection and Introspection: C++ lacks native reflection capabilities. This absence makes it challenging to design classes that can adapt based on their properties or behaviors, limiting some aspects of reusability.
5. Platform-Dependent Behavior: Ensuring consistent behavior across different platforms and compilers can be daunting. Features like bitfields, endianness, and even some undefined behaviors in C++ can affect the portability of reusable classes.
6. Decoupling and Dependency Management: A reusable class should be as decoupled as possible. However, ensuring minimal dependencies while maintaining functionality can be challenging, especially when integrating with legacy code.
7. Versioning and Backward Compatibility: Over time, as the class evolves, maintaining backward compatibility becomes crucial for reusability. Ensuring new versions of a class do not break existing applications is a persistent challenge.
8. Balancing Flexibility and Simplicity: Designing a class to be universally applicable can make its interface and implementation complex. Striking a balance where a class is both reusable and straightforward is a nuanced endeavr.
9. Thread Safety: With the rise of multi-threaded applications, ensuring that reusable classes are thread-safe is paramount. However, integrating thread safety mechanisms can introduce performance overhead and complexity.
10. Standardization and Documentation: For a class to be reusable, developers outside its original project should be able to understand and employ it. Comprehensive documentation, clear naming conventions, and adherence to coding standards are essential, yet often overlooked or inconsistently applied.

In conclusion, while the ethos of C++ offers a fertile ground for the development of reusable classes, the path is laden with intricate challenges. Mastery in designing such classes demands not only a deep understanding of the language but also a foresighted approach that anticipates potential pitfalls and navigates the delicate balance between generality and specificity.