Vyndree has documented and proven successes with 3 elemental and 1 resto, so I call that the safe bet. The 'holy trinity' is always safer. She says she got to 70 with 4 elemental then started hitting walls. Swapped one to Resto and it was a new lease on life.

I'm hard headed and lower level (55 atm) so I'm still running 4 elemental but I'm starting to stack my remaining 20 talent points (after getting ToW) in Resto and I do healing rotations.

Your play style will morph as you go anyhow, so I wouldn't get too hung up on setting it in stone. I'd just run the 4 elementals, plow through everything until you hit a wall. Then figure out how to get around the wall. It's not a big deal to change spec later, it IS a big deal to have to reroll a class.