At least one of the shamans should be doing nothing but being a spirit battery... gemming pure spirit and all. Both trinkets should be spirit trinkets. The other could do the same or could go a more throughput focused build. Shaman heals are best suited as tank healers currently.
You guys will actually have a very simple time healing all fights with the monk. Tortos will be pretty simple since you have a major healing cd on every stomp (revival, 2 htts). Megaera will be where both shamans will be incredible.
Also, shamans can do a hybrid offheal thing on a few fights with conductvity and elemental spec, main ones being council and ji-kun because chain lightning. Have one shammy definitely do that on ji-kun with your egg group.
Your most difficult fight will probably be horridon or durumu or animus as shamans are viable for the rest.
Their shaman's and monks they don't have anything but healing throughput
With all the nerfs the bosses have received of late you'll find it much easier to 2 heal, currently we 2 heal everything we've killed and we're working on Iron Qon, with the exception of a boomy helping heal on Ji-Kun.
But then we run a Pally and Druid heals and they work very well together, and the rest of the raid uses their personal cd's to help out
Being honest your best to make one of the shamans dps and get a disc priest or pally to replace them as heals
Your healers might not have very good synergy, but at the end of the day it all comes down to how the raid as a whole meshes and what tweaks you can make to the strategies to overcome when you something lacking