I took up Raptor farming today, and most my drops were Fruitcakes and damn Snowman Summoners. I saw numerous people in Rata Sum asking for leechers, so my guess would be that it does help people.
Strange thing is that if I do it without a leecher my drops suck, and with I score multiple items. Haven't done it as long os some of the posters before but I think they have way more exp then me with this. Maybe I was just lucky with leeching or unlucky without them :s
Hate to say it again but no1 cept anet can answer.
Conidering gw drops are luck based and so many factors to affect it - how many times has x done run in succession an so on.
Without offending ppl its a bit like God - No1 can prove he exists and no1 can really disprove it so theres always going to be the pro and anti ppl.
Ask the 6 gods and they will plainly say - we dont know as anet hasnt revealed it to us :P