Your basic composition is identical to my own. If you plan on eventually raiding Ulduar, I'd really recommend two priests. The mass AoE healing is endlessly useful for keeping things simple and straightforward. I'm also fond of having a second paladin; the second set of blessings is a nice bonus.

Lately I've been toying with the idea of dropping two of my shaman for either two additional priests or a priest and a druid, mostly for multi-role purposes. The druid would alternate between tank/dps roles and the priest would be there to cover additional AoE healing if ever needed and otherwise be in shadowform. I'm not certain how convenient druid tanking is while boxing nor am I sure about how much ( if any ) this would reduce the tank burst damage that I often find myself falling victim to in Ulduar, but any improvement would be welcome.