30-40% is a bit high...since it can only be used on a PC, let's say the PC playerbase is 50-60% of the total installed playerbase. If about 25% of THAT 50% of PC users actively raid, and we assume all raiders use a parser, then the 25% of the PC installed base of 50% would need to account for 30/40% of the entire subbed population, which I am really fairly sure isn't the case. I don't believe the amount of people raiding in the game on PC is equal to 30-40% going by clears alone (from census data and other sites).

Plus, I'm not even sure if they could identify who uses the parser in the first place, and if they did, I very much believe they would issue a mere blanket warning about using it. While they may not be able to tell who uses it, they probably can very well disable the ability for it to work. Still, saying that banning those who use a parser would make SE lose 30-40% of ffxiv's subscribers is quite a long reach ^^