I have already commented enough of my views about Holy in raids since patch, but I've not said much about 5-Man. And as it seems some are struggling with them, I'll try to give a few hints about how to handle a rushing instance group. And trust me, my guildies are not stopping for more than bosses ... and most of our dpsers seem to be completely suicidal to me lately, so healing 5-Man can be intense :P
First, you should have the right spec. I advise you to read my earlier posts:
Patch 4.0.1 is going live. You are not prepared!
First impressions on 4.0.1
You should have a 31/2/3 spec with an emphasis on Holy Shock and Word of Glory. The reason for that is that they will be your main tools for any 5-Man.
The ToR style is perfect for instances, it is very rare that your tank will need more than the Beacon influx added to the occasional direct heal used to get Holy Power. Perhaps more will be need if your tank is slightly low geared or if you're into heroic HoR, but on a regular basis you'll be perfectly fine with a regular ToR build.
That means that you will be doing that, with that rough priority order:
1. Beacon of Light on your tank;
2. Use Word of Glory when you have 3 Holy Power stacks (and only 3 !), repeat if you get an Eternal Glory proc;
3. Use Holy Shock on cooldown, if only your tank is hurt, use it on him, if anyone in the group is hit, and unless your tank is in critical, heal the group member (+1 Holy Power);
4. Direct heal your tank with a Holy Light if you're not in a hurry, with a Flash of Light if you're in a hurry, with a Divine Light if he's very badly hurt (+1 Holy Power);
5. Direct heal one of the group members if your HS is on cooldown and you don't have 3 stacks of Holy Power and it's urgent.
Now if you have enough crit/haste your HS/WoG + Beacon will handle 75% of your healing. I don't think you should have any mana issues with this "rotation" as WoG is free, can sometimes be used like 3 times in a row thx to Eternal Glory, and because HS is our most efficient heal per mana skill.
If your mana is going down, use Divine Plea while running between pulls, but that should really not be an issue. Don't forget to judge for speed and a bit of mana too.
If you are still not at ease, I suggest that you test this "rotation" on yourself for a little while, it's easy to maintain once you get used to it, as any dps "rotation" (yes several paladins are saying we are now pew pew dpsers ;p).
Have fun and if you ever encounter issues, don't hesitate to comment here :)