A couple of months ago, my tanking partner of over a year decided to take a break from WoW to focus on real life. In my guild, our policy has always been real life over the game, so there were no hard feelings. Although I was happy for my raiding buddy, I wasn't looking forward to recruiting a new tank. After tanking together for so long, we could predict what the other would do and we worked very well together.
I eventually recruited another tank, but didn't feel as comfortable as I was with my old partner. "It will take time," I told myself. I was just making myself feel better, and to be honest, I still don't feel a connection with my new tank partner. I've not had fun raiding lately and that's a bad sign. The social interaction in WoW is as big a factor in why I play as the content is.
How about you? Do you have an in-game friend that you team well with? If you raid, how important to you is having a connection with others in your group? How do you feel when that dynamic changes, and what do you do if it does?