First, some of you guys are acting like maximizing your potential using a parser takes a huge amount of time. It takes actually very little time, hell you could probably do one dungeon/raid and learn your best rotation. I figured out mine in 3 boss fights from just asking one of my party members how my numbers looked. From a tank perspective it is very helpful for me to know where I am standing which can range from 90dps(mobile fights) to 125dps(Stand there fights). I didn't even really spend any extra time figuring it out since I just asked my party member where I was and continue to do so from time to time to ensure I am putting in the most I can. So if I am doing a raid and someone pulls agro I can verify if-
1. I am slacking because I know where my numbers should be. or
2. The DPS just overrode my agro with some huge hits. This allows me to immediately correct the issue, either by telling the dps I was behind where I should have been on threat generation or they just need to watch it.

Parsers are incredible tools that give you a quick overview of a fight. Most of the people I have encountered in raids that do not approve of them are players who cant use abilities and move at the same time while dodging enemy abilities(Which drastically affects their performance though BLM Wouldn't be even a factor here) or overall don't have any sense of situational awareness. However with that being said, outside of raids parsers should not even be used except for personal improvement. I have never used a parser in the past on mmo's to belittle someone in a dungeon. People are there to gear up or farm, so you will have characters that just hit 50 and may or may not have figured out their class 100% yet.

If SE wants to make a smart move they should just implement it into the UI for 8m full FC party or 24m FC raids and not 4m light parties. Of course from a raid perspective you would need DPS/Heals/HPS/Overhealing/Damage Taken/Damage Done/Dispels cast. While other addons are nice, I don't think SE should allow them in game like wow did and opens up other issues(cheats). It made things too easy and took the challenge out by telling you where to walk and all.