I'n all honesty, if you are looking to get into ops and raiding, you are making your life difficult by not wanting to use a voice chat program.
No matter how casual a guild, if you try to do ops and are completely new to them, it's much harder to understand what is going on in the mechanics by reading text about it (if they explain it all in text).
Most guilds that do raids (that I know of) pretty much require a voice chat unless you know the fight by heart and can do it WITHOUT a voice chat.
Best of luck in your search. I hope you find what you are looking for, and don't get too fustrated in the process.
On a side not, for several guilds that I've seen, if you don't have a mic (which some don't), you can still use a voice chat and be able to listen to what's going on.