Dis Priest Questions

Hello guys, ive got some questions about dpriest. Its my first healer toon ever. In ToC25m i did really well (skada shows me top all the time except in fraction and last boss, and j reset data on each boss). The problem comes in 10m. Which healer will be the best combo for dpriest and like i normally do i concentrate on tanks, as i think dpriest is more of a tank healer. My doubt is what and how much should i expect from myself in 10m raids?. I try to fill up healing raid party in between the tanks, but still we went on a wipe repeatedly. The raids normally compose of:
Tanks : warrior + dk
Rdps : boomie, mage, lock
Mdps : dk, pally
Healer : me, shammy/dudu
All 5k+ gs. (a suggestion on 10m composition wull also be nice)
How can i tell the other is not good or i am not good in a 10m.
Skada shows both absorb and healing combined. As per my understanding, the other healer should still be higher than me. But how much lower then the raid healer is expected of me. Or my whole concept is wrong. Btw i dual spec with shadow for farming mats and all so i cant or dont like to have holy spec.
Please help out. Thanks.

Disc priest is primarily a raid healer, not a tank healer. The whole philosophy of a disc is to shield all raid members, to reduce their damage taken. They go well with holy paladins, and i'd say resto shamans as well. Holy paladins are tank healers, and with him you'll be able to focus on the raid, shielding them, and the paladin can simultaniously heal the tank while healing the raid to full. To be able to play disc well, you should really try and know the fight and when to expect someone to take damage, so you can shield him beforehand. Although, for 10 man, disc priests aren't as popular, since holy pala + resto shaman are pretty much the best healing combo. But in 25 mans, there always needs to be a disc priest because his shields help immensly.

About Skada, disc priest is pretty much always top healer, because damage mitigation > healing, but its not the best proof a healer is good or bad.