If your tank/healer is geared, shackle is almost entirely unneeded. The guild runs I go on, only use shackle for the trash pull to Opera that freeze the tank -- but you can instead use grounding totems.
It's possible to 1 tank + 1 heal most all of Kara, with maybe some offspec tank/heal on certain fights, but you'll need serious gear to pull it off.

If I had to choose 2 healers for Kara I'd pick Resto druid and Holy priest, HoT's and group heals are so much easier than playing health-bar-whack-a-mole.