Well, this is a tricky question to answer on the official forums because, officially, parsers are not allowed. However, there's a sort of don't-ask-don't-tell thing going, where SE doesn't care that much as long as you aren't harassing other players.

There is a parser that can do things like graph a 30s rolling average (or whatever time period you prefer), and can display an overlay so you can monitor your DPS in real time. I would ask this question on reddit or another place so it can be answered more completely.

In fights with mechanics, the data definitely needs to be put in context, and RNG selecting you for mechanics often can lead to lower DPS. You can still monitor where it was before/after mechanic but when looking at the whole encounter, yes, your raid team does need to acknowledge when someone had a bit less uptime because of it. The encounters are tracked and logged very thoroughly, but the programs do sometimes make you go digging for the info.