For the record though: I'm actually pro-electoral reform without the referendum, but I always entertain the counter-argument of why a referendum can be justified or why a direct-democratic approach may be necessary for certain policies.
Insofar as majority power is concerned, I'm not sure if I share the same viewpoints regarding minority power in government: oppositions have always held the government's feet to the fire, majority or minority; media and news outlets are good checks on government power; and lastly, activism, demonstration, and protests are often stronger than government policy.
To be a little off-topic, I don't feel pure PR is the panacea for democratic societies. I can point to examples such as Germany, Israel, and so forth that have had coalition governments for extremely long periods of time -- where the leading party has always been the same, with slightly different faces at the table. Democratic renewal is essential to avoid stagnation, which is why I've always supported some sort of mixed electoral system, combining both individual candidates and party lists.