Both ね and でしょう can be used to form tag questions to confirm an opinion like so:
1) 疲れたでしょう。 (more of a guess based on evidence / polite)
2) 疲れたね。 (more forceful / the speaker is more certain)
3) 疲れたでしょうね。 (forceful, but polite)
For the purposes of these questions you can imagine that these sentences are spoken to someone who has just done something physically exerting (like moving boxes for 7 hours).
Am I right about these guesses? Can anyone elaborate more?
When a speaker says でしょう, he or she puts more weights on the guess or asking.
When a speaker says ね, he or she expects an agreement from the listener. It is slightly more assertive (or forceful as you say) than でしょう. If you want to add the politeness, you can rephrase it by saying 疲れましたね。.
However, でしょうね is more assertive than the two above, and the speaker might even not expect the listener to respond.
Note that 疲れたでしょうね。 is slightly unnatural. I would say お疲れでしょうね。.
