Thinking of jumping on the bandwagon with shaman

So now that I've got my first group (which is awesome, btw), I'm thinking of jumping on the bandwagon and doing an all shaman team (5 of them). I've always loved shaman, i love the burst damage and the viability of a hybrid class, and being able to solo most pve stuff. I want to make it a long term project, maybe by expansion have a group ready to go.

I know I can RAF a group up to 60 in under 24 hours played using one of my warlocks to boost. So I got that covered. But having just done 60-70, which was incredibly painful, this is my main concern.

Can a 5x shaman group grind instances quick enough that I could do 5-6 hours per level in the 60s? I'm talking 120k per hour sustained. I figure it's gotta be possible - I was grinding BF with 4 clothies and a voidwalker tank and pulling 85k per hour. Since this will be long term I figure I'll be able to work with a lot of rest XP as well (including the 1.5 levels I'll have at 60 after RAF).

Also, what benefit do I gain by having a paladin as the 5th instead of another shaman? I've seen a lot of groups do this, but at the same time I know people run heroics with 5 shaman.