I think you are referring to diversity, not obscurity. Diversity does indeed increase the resilience of the network, but there will always be enough common factors across the board, that diversity alone will not suffice.

In the end, the software that we depend on, must be reviewable by anyone who is concerned about it. A prerequisite for that, is that software should be as small, clean, and simple as possible, to encourage such scrutiny. IIRC, the real problem with heartbleed, is that the OpenSSL codebase was a mess, and no-one wanted to work on it.