Yeah, ToC as a healer is pretty easy, although most guides are written for the entire raid and it can be difficult to distill them down to the essentials. Some general things for a healer, without all the rest of the stuff:
Beasts:
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[li]Magnataur: keep an eye on the health of guy who gets a kobold on his head;[/li][li]Worms: if you get fire on you, go to the guy with poison on him, and vice versa. Watch out for the mobile worm, it has a frontal acid spray;[/li][li]Yeti: when everyone gets thrown to the wall, if the Yeti is looking at or near you, run along the wall to get behind/to the side of him.[/li][/ul]
Jaraxxus:
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[li]Heal the guy with incinerate flesh (DBM will warn you);[/li][li]Run in a straight line to the wall and around the edge of the room if you get legion flames on you (DBM will warn you about this, too);[/li][li]Get out of hellfire.[/li][/ul]
Faction Champions:
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[li]Try not to die. Don’t stand there like a goober if something is hitting you - running away from it will frequently get it to switch targets, and may prevent some hits from landing if there are hunter frost traps, earthbind totems, or other snares on the target.[/li][li]If you have time, and see a hostile totem, whack it… DPS classes are notoriously bad about hitting them, in my experience, and nothing makes this fight take longer than a rampant healing stream totem working on all the mobs.[/li][/ul]
Twins:
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[li]There are dark portals and light portals: click the one that’s the same colour as the Twin you’re standing near, or whichever colour you like if you’re in the middle;[/li][li]There will be orbs floating at around the room - avoid orbs that are the opposite of your colour (moving your camera to a top-down view can help);[/li][li]Click the other coloured portal when DBM yells at you.[/li][/ul]
Anub’arak:
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[li]Watch out for the spikes on the ground when he submerges underground (they will insta-kill you if they touch you);[/li][li]If the spikes are chasing you (DBM again), run away from the spikes and get a patch of frozen earth (a white spot on the ground) between you and the spikes;[/li][li]At 30% he does a leeching swarm ability - don’t heal anyone to full except the tank, try to keep everyone around 20-30% health, because the more health people have, the faster Anub’arak steals it and heals himself.[/li][/ul]
Also, imo, ToC-25 is easier than ToC-10 simply because there are more healers to share the burden, and one or two bad DPS won’t kill the raid like it will on a 10-man. YMMV