No, enmity list is not the same as a DPS meter. No, you cannot recreate logs with the in game combat log and a calculator, no one does this. If it were viable they would do that instead of injection.

And the sites being default running on everyone affects people's personal enjoyment when it's used to beat new ones over the head with their performance and used as a measure of who is allowed in PFs for new content. FFLogs and Tombstone are a prime example of a mod that has gone so widespread people aren't even afraid to talk about using it and aren't afraid to use it against other players maliciously.

If Mare crossed the line, those sites definitely cross the line.