In fact, without official parser, there is already the "right/wrong" way to do (right = the one that allow the team to do the most damages.)
and this exists also WITHOUT any parser.
The parser is just a tool to see how much damages (hors heals). Like you can use some tools to know how much the table is wide, the temperature outside or your own weight.
Parser are already in use, parser are already uploaded on a site, where some peoples' damages are already without they know it, even if here they say "parser is baaaad". This tool that only displays DPS information are already in use.
Speaking about toxicity it could generates, or all risks due to parser is just forgetting there is already parser, and they are already used a lot...
For "see wow"
Yes, WoW get some stupid ilvl requirement for some content... FFXIV also
Yes, WoW get some many selfish people... FFXIV also
Yes, WoW get some toxic players venerating god damagemeter (or d***meter also) and... nearly the same in FFXIV without any official.
But, first wow didnt see ilvl (needed informant) and it become crazy with "gearscore addon" (shitty one) and then... people did regulate a little. It is not a "perfectly happy situation" now but far more better than back in WOTLK and this addon.
Selfish people are due that both game can be played solo for most part. And it makes people doing even more thing like asking stupidly high ilvl or being damagemeter-nazi.
God damage meter? Same, first people asked so high sometime, and now, even after 3-4 wipe in LFR people are not kicked due to low damages, or the abyssal damages. But when you see fight like faust (A1S) a fight which only difficulty was the DPS needed. And many party didnt even go through it... What is the solution except seeing who doesnt get enough damages? Same when you hit enrage at 20% life left on boss, but the party did manage perfectly all mechanics...
Toxicity seems most of time here, on WoW forum and other places a word used to complain you were kick and dont want to evolve and see yourself what you maybe did wrong... Easier to complain that people are toxic around you i think.