Despite the high-level of automation offered by model-checking techniques for proving that a system satisfies its specification, if one property is violated the designer is left with a counterexample trace to understand. In this paper, we overview ten families of techniques used to diagnose a system relying on traces. However, whereas these techniques are highly effective and are largely used, they are either not yet available in the context of model-checking or they are not adapted to the particularities of this verification technique. To address this, we have identified three very challenging problems hindering the concurrent systems diagnosis process. Through this analysis we have defined a roadmap for future research directions in our team.