I use both task scenarios (steps a user takes to accomplish some goal) and decision trees (questions the user or system needs to ask to accomplish the goal). One is task centric and the other is process centric, but both are focused on understanding the goal and how to acheive it. There are too many ways of getting to the same means, you must identify the goal, you must identify the process(es) used to achieve the goal and the tasks within the process. You can work bottom up or top down. Sometimes I watch people work and record their tasks, identifying the formal or informal process they use and the end goal, whether they stated it or not. Sometimes I start with the business stakeholder, understand what they want to acheive, the process by which they might make it most effective and then devise the tasks most effeciently.
Both of theese techniques help you drive effeciency and effectiveness. Neither of these help you be intuitive or consistent. You still need to turn the stories, personas, tasks, scenarios, or decision trees into pictures that make sense and follow rules.
Who cares which techniques or artifacts you create? If you are actually observing, collaborating and working with your users and stakeholders you know you will be designing the right thing.
Your sketches/pictures/mockups/prototypes will tell you if you talked to the right people and have the right goals.