At my dojo we are doing regular jiyuwaza (multiple attackers with preset attacks attacking one defender who must evade) amongst the 6th, 5th and 4th kyus, even unranked people sometimes get involved.
The speed is regular practice speed and much emphasis is placed on delivering clear attacks with good follow-through. And footwork on the part of the nage to evade the blows.
Our jiyuwaza practice is not really pertinent to the issue because the emphasis is still on evading and moving and not technique but our instructor is constantly assuring us that as we grade and as our skill levels go up things will start going harder and faster.
I think the slow build-up to fullspeed randori is very important and I am grateful that we are getting it where I practice, I am only 6th kyu so I have another 5 or so years (I hope) before hitting shodan so hopefully by that time I will be ready for it.