Beginners: How Many Tasks in Class

Context:
We teach classes of beginners. They learn about Microsoft Office (mostly Word 2000) an Internet Explorer.
Most of us stick to the ratio: one task done with a trainer (fully explained, of course), one done by students on their own and then analyzed by the group (the trainer leads the discussion).
But my feeling is that one or two assignments should be given to do by the students on their own, with the trainer to take part only if invited by those who need it.
Question:
Do you think that tasks for the students to do entirely on their own in class are really worth doing?
Thank everyone in advance. I always rate answers.