I have to wonder how much of the issue is server-specific. Like Qwyxzl says, on Silverlode creepside is less clique-ish now more than ever, so wargs tend to get invites, especially at r6 and above.
Warg packs flourish on Silverlode BUT they will rarely engage even or greater numbers, not that it matters here.
I would try to get known among the warg community first, post pertinent info in OOC and get seen. Sometimes it's just about people being familiar with you and recognizing the name.
On freepside on Silver when a new name (that I haven't seen in the moors before) joins the group something way in the dark corners of my mind mumbles "spy".
My experience is that I can (and do) solo a lot but I will always get invited to a raid, even if I don't ask, but after 7 years I am considered a fixture. Fixtures get invites, r5's could have been r0's just a week ago. get seen, show yourself as a valuable contributor and a fearless fighter, you'll get invites... or roll a warg on Slode so I can set fire to your fur and sizzle your drool!
[center]Irin r8 Hunter // Arngar r8 Burg // [b][color=red]Akthuri r15 LM[/color][/b] // Vishus r5 Captain[/center]