Dont give up on them, sometimes it could be your bow or some other factor... I have Muzzy 3 blade 100's and a bunch of Magnus stgers 2 blds 100's, both heads shoot exactly the same as my 100 gr FP's... The Magnus naturally get much more penetration, and fly a little bit quieter I have noticed, but if you cant make em work, by all means dont use them, buy serveral brands and try some out, see what works best in your bow/arrow combo.

Make sure nothing looks like it has moved (sights, rests, nocks, ect..)
I usually get my stuff set just right, and take a marker and mark on the sight, rest, ect.. to give you instant feedback if something has moved a little bit..Try this when you get it figured out, it will save you some hearburn later on down the road.