So Jess is our main tank. She likes to tank and spank while K heals with zeal (rhyming, FTW!). Jess has a special relationship with K... you know that tank-healer bond that comes after running many instances together.
Jess and D were actually telling me the other night that since we've been running together for so long, the two of them can predict how I'll heal and where I'll be in relation to them. So when I'm getting hit and need to spam my emergency help me macro which yells "K is getting beat on! Help her!", they pretty much know where I'll be to come save my squishy ass.
So at first I was kind of surprised (am I that predictable? maybe I should change some things up next time to make it interesting...), but I guess this is what makes groups who have run together for a while more successful. Not only do we trust each other and not get crazy angry over mistakes or a wipe or two (because as D says, you're not having fun unless you're dying), we understand each other's playing styles and can predict what the others will do.
I think this kind of experience can make up for non-traditional class makeups. We've run a lot of instances with a warrior, druid, and 3 rogues. Yup, no ranged dps. D calls us the strike force. They like to get all in there and get their hands dirty.