http://www.wowprogress.com/achievement/5121_25
685 25-man Sinestra kills up to today (that includes whole lot of facerolling with FL and DS gear), for let's say 32 people per guild = 21920
http://www.wowprogress.com/achievement/5121_10
1374 10-man Sinestra kills with average of 12 ppl per guild = 16488
25+10 size players together = 38408
That's about 40k players out of 10 million who has been able to finish T11 up to today, or less than 0.5% of all players. So yes, raiders capable of doing heroic modes are extremely tiny minority and catering to 0.5% of your potential customers is a suicide for any kind of business.