we don't disable both TR's if only one is broken. we are however very careful when we use just ONE.
This policy is also depending on local authority regulations. Since the S7 778 accident in Irkutsk, the Russian AR-IAC does no longer allow to disable T/R asymmetric. So either you disable two T/R, or you are not going to fly. Traditionally the Russians did not know an MMEL, so it is only possible for western type aircraft to disable anything and still fly.