Not sure if this has been asked/addressed, and I'm at work so it's easier for me to peek at the forum than most other research...
Question: For the guild-based achievements like "you and a party of your guildies run through the following heroics/raids", what does the group size need to be? Can it be me and 2 guildies run through Gruuls Lair and get credit for it? Do 5-mans need a full 5-man party of guildies, do raids need an appropriate number of group members (10, 25, 40) in order to earn the guild run achievements?