I tend to think of it as being that an author has a contention, and they use an overall strategy to convince the audience of the validity of the contention, and this is reflected in what devices they use and how they are trying to position the reader.
An example of a strategy would be that the author wants to discredit the opposition's argument, and to make their argument seem irrefutable through the use of statistical evidence, facts, and the opinions of experts.
It is up to you whether you want to introduce the strategy first, and then focus on how the devices complement it, or whether you want to analyse the devices and deduce the author's strategy from your analysis. Looking at the author's strategy is just a method I use in order to create a more cohesive analysis. It allows you to show the logic behind the author's choices, rather than simply analysing devices in isolation, which is a wholly reductionistic approach, you do still need to do that, but you should also aim to, if possible, demonstrate an insight into how the piece works as a whole, which requires you to use a holistic approach as well. Note that you don't need to be relating every single device back to the author's strategy, but you should be aiming to give us a sense of how everything fits together.