The former Barcelona coach received his fair share of criticism after Bayern's Champions League semi-final exit at the hands of Real Madrid, but Rummenigge believes the 43-year-old did not go wrong anywhere.
"After winning the treble you might tend to think you don't need to change anything and all changes are wrong. But Pep has changed quite a few things. And all the changes he made were right," Rummenigge told the official Bayern website.
"He got rid of the two defensive midfielders, he put Philipp Lahm in the holding role, the team played higher up the pitch and they pressed more than in the previous season. He set the team new challenges."
Rummenigge then went on to stress that Guardiola has been performing at the same level as during his time at Barcelona and has hailed his ambition to win it all.
"He hasn't surprised me at all. He's shown the same level of quality as he did at Barcelona. Pep is a wonderful coach with a clear philosophy, a clear plan - and, as you saw in the cup final, he's a coach capable of springing a tactical surprise that causes the opposition problems. We're really happy with him.
"He had to get used to a different culture in Germany and here at Bayern Munich, and he also had to learn a new language. You can't forget that. But I think the only thing that annoys him is not winning the Champions League. He's incredibly ambitious."
Guardiola guided Bayern to the domestic double in his first season in charge of Bayern.