Isn't it redundant to have Versions as well as Time Machine?
No it is not the same:

Versions: It is for different versions of your documents. You change something in your document and you can revert to an earlier version. This is not possible with Time Machine in this granularity. 

Time Machine: It is for backup. It handle the case that you need to recover from a hard disk crash in your mac. You can't do that with versions since versions saves your changes on the then defect hard disk. 

So they have their purpose since they „solve“ different problems.