Perfect forward secrecy (http://en.wikipedia.org/wiki/Perfect_forward_secrecy) is a desirable property for encrypted communication. While TLS includes some ciphers that have Perfect forward secrecy (PFS), Internet Explorer doesn't implement several of them, and gives low priority to the ones it implements (probably because they are a bit slower).
Moreover, most of the implemented ciphers are recent ciphers based on elliptic curves. Supporting more old-fashioned ciphers would 1) make PFS work with RSA certificates and 2) be safer in case a flaw in elliptic curve ciphers is found.
Please add support for TLS_DHE_RSA_WITH_AES_128_CBC_SHA256 and TLS_DHE_RSA_WITH_AES_256_CBC_SHA256 (as defined in TLS 1.2), and an option to prefer PFS over performance.