Here are his stats vs some of the top managers of our era:
vs Ferguson: 7 wins, 7 draws, 2 defeats
vs Wenger: 5 wins, 4 draws, 0 defeats
vs Ancelotti: 1 win, 0 draws, 1 defeat
vs Benitez: 6 wins, 3 draws, 4 defeats
vs Van Gaal: 2 wins, 1 draw, 0 defeats
vs Pep: 3 wins, 5 draws, 7 defeats
You can see that he has a positive record pretty much against every top manager (a spectacular record against SAF and Wenger) bar Pep. Pep is also the only manager I rate higher than Mourinho.
So yes, Mourinho is a very good tactician. Boring, but very good. You can't have his record of trophies and these stats against some of the top managers, without being a very good tactician. Not a revolutionary, not innovative but he has implemented very well his tactics.
I think that how a manager does against other top teams/managers is a very good (though not complete) way of judging how good that manager is tactically. For example. Ferguson wasn't ever the best tactician and he has negative records against almost every top manager (Del Bosque, Van Gaal, Hitzfeld, Guardiola, Mourinho, Ancelotti) bar Benitez and Wenger (in fact, only on 2009 or so he managed to have a positive record vs Wenger). He is regarded the best ever (or near it) because of his other strengths, but it is fair to say that tactically he wasn't great (obviously he was very good, you can't be the best without being a total package, but just not as good as he was at other things).
On the other side, tactics are one of the Mourinho's strenghts. That and the mentality he installs. He isn't the best coach, clueless at developing new players but very good at winning.