I found this little gem and it is exactly what I was looking for. A way to filter out "lf trash" groups.

http://www.curse.com/addons/wow/premade-filter

There is extended query syntax for title and comment fields. You can use these prefixes before the words:

plus(+) or no prefix at all to add a word to must-have list
question(?) to add a word to must-have-at-least-one list
minus(-) to add a word to must-have-not list
So you can type something like this "Highmaul ?Kargath ?Butcher -tank +normal" to find anything that:

has both "Highmaul" and "normal"
has "Kargath" or "Butcher" or both
has no "tank"