For those of you thinking of setting up a parser to measure DPS/HPS for your group, or for yourself, Fold of Collision has set up a guide explaining all of the features and options available in the ACT FFXIV parser plugin, as well as a step-by-step guide for getting you started on making useful parses ^^
LINK
It also includes setup guides for nice and pretty overlays, so you don't have to use the default horrible miniparse window.
Parsing through ACT is technically against the ToS, because it reads memory, but as long as you don't be an ass about it and yell at people ingame because of low DPS numbers, you'll be fine. It's not something people get banned for unless they use it for harassment, in which case they get banned for harassment.
For PS4/PS3 players, ACT is sadly not an option. However, I'm (almost) always available for a personal parse on a training dummy, or if you happen to be in a group with me feel free to ask for your numbers (ideally in teamspeak, or just ask for "parsley" ingame) since I'm always collecting data.
Parsing is a good way to see improvement in yourself, and with constructive criticism, see improvement in others as well. Oftentimes it's one of the only ways to really see what exactly went wrong when a pull goes bad! I'd like to encourage each group to have a couple(two or more people, since it's not perfect by any means) dedicated parsers, and use the data to improve overall performance.