The idea of the two round burst the Russians use is to hit the same spot, or very close, twice and defeat body armor. That is why it fires at such a high rate. My understanding is it has proven quite effective in tests.
HK33 and HK G36 do have variants available with the two round burst. I don't think they are close to the most popular variant and I wonder how popular they are or what major organizations have purchased them. At 700RPM there is not the same double hit effect.
For reference I believe the fastest cyclic rate on an AR type full auto put into service was a little over 900 RPM and that was slowed down as it was thought to be too fast.