DoT tick damage is not present in the logs at all, and thus a parser cannot read DoT damage. The parser out there currently attempt to solve this by simulating the DoT damage - which leads to results that are more accurate than completely ignoring them, but overall still very much inaccurate. The more a job's damage is based on DoT damage, the more inaccurate they parse.

SMNs, BRDs, and BLMs have seemingly lackluster DPS values on parses for this reason.

We won't see reliably accurate DPS parses until we have add-on support.