Database vs SAN vs Network Encryption
If we presume that the two encryption methods are secure by themselves, then having double encryption will not introduce any weaknesses. Sure, the security of the encryption may be smaller than key size of the keys combined, but if you use two different keys then the security should not be smaller than the key strength of the smallest key used.

Of course, if the same symmetric key (and IV) are used then you could get into trouble as for some operations the encryption and decryption are identical. This is, for instance, the case for stream ciphers and counter mode encryption. However, if the same symmetric key is used for two different purposes then your key management is the issue rather than the methods of encryption. I presume though that key reuse is not performed as the SAN admin should not possess the TDE decryption key, according to the info in your question.

In short, as long as you don't presume that performing additional encryption makes the initial encryption stronger, then you should be OK. The double encryption problem as you state is mainly concerned about the fact that the key strength may not double even if you encrypt with two separate keys. But as far as I see, doubling the key strength is not your goal in the first place.