Do any decision problems exist outside NP and NP-Hard?
If $P = NP$, then any non-trivial language is NP-hard, and any trivial language belongs to NP. Hence, we do not get anything which is neither NP or NP-hard in this case.

If, however, $P \neq NP$, then there are languages which are neither in NP nor NP-hard. 

For example, we can consider the language $\{1^n \mid \text{the } n\text{-th TM halts}\}$. As this language is not computable, it is clearly outside of $NP$. As this language is sparse, $P \neq NP$ together with Mahaney's theorem implies that it is not NP-hard.

If we want a computable counterexample, we can take a language $L$ that is not in EXPSPACE. We number all finite words in increasing order as $(w_n)_{n \in \mathbb{N}}$, and now consider the language $L' = \{1^n \mid w_n \in L\}$. Again, Mahaney's theorem ensures that $L'$ is not NP-hard. If $L'$ were in NP (or even PSPACE), then an EXPSPACE algorithm for $L$ would be available in "Given w_n, compute 1^n and run the PSPACE-algorithm for $L'$ on it."

See here https://math.stackexchange.com/questions/235162/if-an-unary-language-exists-in-npc-then-p-np for a proof of Mahaney's theorem. Note that Yuval speaks about starting with an NP-complete unary language, that assumption is not used - the argument only needs an NP-hard unary language.