I don't think parsers are against the rules. Calling other players out on their dps is however a no go. I personally think using a parser is great for optimizing play. It serves as a good measuring stick and provides a lot of information you can use to compare yourself to other players on fflogs (and try and figure out what they do differently).

Also something that wasn't mentioned but there are some healing patterns that can be used to increase your dps uptime. Might be useful to have some astro mains give you their usual pull patterns on the off chance you could learn anything from them.

All in all, dps is something you should do during your healing downtime. You get to chose when it's right to heal so people won't complain. It only really becomes an issue in content where your group really needs you to dps strong. Like some progression encounters or speed runs.