I think you need to put yourself in RDM's shoes when it comes to understand Chelsea's defensive tactics in the last few matches in the CL.
Against Barcelona. If you try to fight them head to head at their own game, you lose. That is a football certainty, no team can match their possession or passing and trying to play like them will get you played off the pitch.
So you play to your strength, you play in a way that you can win and hope to have a bit of luck. They did that in the semi's. The first leg went to plan and kept a clean sheet. The second leg the plan was to hold on to that lead and they HAD to especially after JT got himself sent off.
In the final they were without their first choice centre back, first choice right back and their first choice midfield. With two centre backs that had been out for 4 and 5 weeks respectively, they are not exactly tested for their partnership nor 100% match fit, with Robben being a danger on the right they wanted to eliminate his threat by double team him hence the extra left back as left wing.
Not to mention the final is basically a Home match or Bayern, and they had 2/3 of the supporters in the stadium capacity. Home advantages is certainly on their side.
No doubt it was a tactical decision to play defensively. To think you would go out all guns blazing with the suspensions to the key players and the conditions of an away match in a final that these players will probably will never see again is somewhat laughable I think.
Chelsea played safe, and they won. Tactically justified. The end.
