After going through some case studies I have realised that the suggested strategy of structuring your thoughts by using an issue tree and/or a common framework first "limits/hinders" my ability to think broad and see the big picture. The fact that issue trees are meant to be MECE makes it sometimes difficult for me to include other important aspects which should be investigated but are either not captured explicitly by the issue tree/framework (e.g. customer segmentation in an otherwise profit-equation based problem) or are not MECE (e.g. analysing growth potential and competitiveness in a market entry case). Consequently, I found myself forgetting to analyse other important areas simply because the issue tree or framework was too specific to capture them.
What really helped me here was to do some mind mapping of all the relevant aspects/areas I wanted to investigate right after the case was presented to me. After that, I determined which of these areas was the most critical one in order to solve the case and focussed on this area during my analysis. Thus, the mind map only served as a "preliminary structure" which ensured that I saw the "big picture" while being able to determine the "direction" of my analysis. Then I would develop a MECE framework for the critical area and anaylse it. A mind map is not necessarily MECE and not as structured as an issue tree. However, it helps me a lot in not forgetting about other important areas to consider in addition to the "key area" which would not have been captured by applying a MECE framework right away.
My point here is, is it ok to use mind mapping first to get a preliminary overview of the situation, identify the focus of your analysis AND THEN continue with developing a MECE structure of critical area identified?
Sorry for this too long question but I just wanted to make sure that you get my point :)