How bad is a Computer Science course that doesn't teach Design Patterns?
There is more to a CS degree than programming and more to programming than Design Patterns. I'm actually an expert in such things and have designed and published a few as a committed member of the patterns community. If I were teaching you programming in some object-oriented language you would certainly learn about and use many such patterns, but you might never hear the names, just the usage as good ways to write programs in a certain set of languages. 

However, I have a friend, also in the community, who is well known and has designed many things fundamental to areas of programming languages who doesn't use the standard design patterns you are probably thinking of at all. The reason is that he programs in LISP and CLOS, not Java and C++. His informed opinion about the design patterns is that they are merely corrections for flaws in certain languages, primarily C++. Many of the kinds of things that design patterns accomplish in C++ are done in more natural ways within Common Lisp itself without needing any such mental tricks. 

So, it may well be that your curriculum is flawed, but not teaching the patters in the Gang of Four book is not the only indicator. (Some of those authors are friends of mine, in fact). 

Moreover, there is more (much more) to CS than programming. Have you learned data structures and algorithms? Have you learned architecture and databases? Have you learned data communications and concurrency? Have you learned to work in teams on large projects? Have you learned to think abstractly and to decompose problems and compose solutions? Those are vitally important too.