I've been using the 5x shaman myself but I have let a friend join me once or twice with his warrior and this is what I've noticed in general.
the play style is different but not impossible to adjust for. I did not make a resto shaman, I always used 4x dps or 5x dps.

almost all bosses are easier with 5x dps shaman.
almost all crowds (in particular large group pulls of 4+ ) are easier with some type of pally/warrior.

I wouldn't rule out using the pally, I'm working one up myself.
You will probably have to have a pally for any type of Kara runs.