I dont personally like disc but when I play it & see it played it kind of goes like this
Since your in a 25m enviorment now you probably wont be doing tank healing much guessing you have a holy paladin or a few. We used 2-3 depending on the encounter.
Prayer of healing is used from mostly what I see. Playing disc as I'm sure you know is about preventing damage, or making it easier for other healers. You basically bubble/shield people.
Nefs crackle about to come up? Bubble up low people & prayer of heal all the groups asap.
magmaw lava spew? bubble people up.
v&t blackout? bubble up & barrier the spot if there isnt one there.
There isnt a huge difference except you'll probably be using penance less than in 10m guessing you werent tank healing. You basically have 5 groups to bubble up rather than 2.
like I said I'm no expert but when I healed 5mans to try out disc for awhile thats what I came up with
Ask them what they expect you to do. Disc can either raid bubble, tank heal or efficiently assist in both, either in the same fight or switching depending on the boss.