Unfortunately, there is no absolute answer to your question. TSM deduplication results will vary depending on the data protected. As mentioned, a TSM environment performing frequent full backups will provide deduplication results that will be closer to those seen in traditional environments. Conversely, if the backups are primarily files then the results will be much less.

In a typical environment, I think that a 50% reduction in ratios is a reasonable assumption.

BTW, TSM users will object to the use of the word multiplexing to describe what they do, but I believe it is appropriate. It multiplexes at the job/client level, though, where other products mpx at the block level.