You're welcome.
While there's no hard set rule for it, there's not a lot of data to prove it useful enough to warrant doing. See here http://divdyn.com/disable-lower-legacy-data-rates/ for one opinion and here - https://getsatisfaction.com/aerohive/topics/disabling-basic-rates-for-802-11n-or-802-11ac for another conversation regarding it.
To me I see it as this. If you're setting your MBR to 12/24, you'd need to maintain a decent enough RSSI/SNR to maintain connected to the APs particular BSSID. In doing that, you're basically indirectly saying that the client would need to stay above a certain signal level and it would rarely if ever need to use the lower MCS rates anyways. The only time it may, would be in a highly congested area where retries get crazy and it drops down to a lower MCS rate and modulation type to try to get the frame to be ACK'd.
Here is a reference sheet for MCS rates and their required RSSI/SNR values - https://www.wlanpros.com/resources/mcs-index-802-11ac-vht-chart/
