Nothing inherently wrong with looking at top x logs, so long as you're aware of the kind of bias this tends to introduce.

Job representation is an important aspect to bear in mind. There are 2.5 times as many SAM logs than MNK logs for Susano Ex, meaning there are more opportunities for SAMs to get lucky runs where crit & fight rng loves them. If you look at top logs you're going to pick up the effects of this. Competing jobs also create sampling bias - if a lot of good players switch from MNK to SAM (for example!!) the data may overestimate the actual gap between the 2 jobs. On top of this FFXIV has a few idiosyncratic effects: balance card, different comps with different synergies. If a particular "meta" develops, jobs not included will tend to suffer in the log rankings - they're almost certainly not as bad as the numbers will suggest at first glance.

You could look at the numbers at different percentiles (e.g. 50%, 75%, 90%) to see if there are obvious patterns.