Does it make sense for a defender to occasionally adopt a slightly inferior line in order to "mix up" the play?
Poker is not a team game; Bridge is. For this reason it is essential that  your plays be reliable at all times when partner has any decisions to be made, potentially or actually. The loss in partnership confidence from not adhering to this maxim is far more devastating than any small gain from mixing up your signals like this.

All too often on Defence the Defenders' knowledge is shared asymmetrically through most of the play. In these cases each Defender needs to trust that, if the situation remains unclear, at a minimum Partner's carding can be trusted to be an accurate guide to decision making. Your suggested strategy confounds this fundamental tenet of partnership confidence.

Further, there are complicating ethical questions about the mechanics of playing such a strategy ethically, Partner and opponents are not only both entitled to knowledge of the carding agreement in place, but Partner must be capable of fully explaining it's nuances, frequency, and constraints to the opponents at the table. Any failure to meet these ethical obligations is an ethics violation subject to the most sever penalties.

If you want to know how top players really bluff you could do worse than to look up a few stories by Randy (Racoon) Bennett