Ive been running my Protpally/4ret team now for over 1 month
Already i am able to clear almost all the heroics (bar the last boss in PoS and the last boss in HoR)
I havent needed a dedicated healer once.
Divine storm + Judge of Light + Lifeward enchant on protpally is more than enough to heal me trough trash.

I also use 3 different /click macros.
All 3 of them have the usual CrusaderStrike, Judgement, Divinestorm
1 of them links to Excorsism with /stopcasting
1 of them links to Flash of light on themselfs with /stopcasting
1 of them links to Flash of light on tank with /stopcasting.

I press the 1st one on trash and bosses for as long as i can
i press the 2nd one when taking to much AoE for divinestorm to heal up (used a lot before i was geared, now i hardly use it anymore)
i press the 3rd when i want some extra heals on the tank withouth interupting their dps.

besides that i use ISBoxer which allows me to pass mouseclicks for selected areas together with Grid addon and Clique addon.
This allows me to click on the Grid frame of any pally in need of heals when i need to.


But yeah a dedicated tank wil make things easier, but imho with 4 rets who needs a healer ?
Same as Prot/4shaman some people like to run them all elemental.
Once your tank is geared enough he hardly needs healing in most heroics.