you are right holy radiance is a mana drain, but the tests yesterday and today hardly made me use it, only when the whole raid got massive damage burst its cast once and seldom twice and thats fine in terms of mana use, but still helps the raid recover a little faster
the holy radiance could be tuned down just a little to say 60, but i strongly beleve it should not be disabled, in dungeon you are the only healer and you sometimes realy need the extra health boost from holy radiance and thats why the setting is on 5 units
the reason gardian is on 40 is with these settings you be casting the expensive flash of light by then, you get that, but sometimes 1 flash is enough to get your buddy above 50 again and then it was a waste of the gardian cooldown, in my experiance 40% is as low as your party buddy's must get, this gives you time to recover from stuns, interrupts silences and stuff you might not think about can happen to you as a healer
Divine Protection is on 80 (i assume you are talking about that) and is a choice, i think the 1 minute cooldown is short enough to use it below 80, do not let ppl tell you wat they want you to do with your cooldowns, do wat you think is right, saving divine protection (or any cooldown for that matter) for a moment that might not come is a waste also
i understand there are more ideal settings, but this is not an ideal game, these are defaults to use for PVE in witch you normaly can not fail, these settings are for ppl who do not know wat a holy paladin is or can do, but want to play it in one form or another
i think we can debate about the best settings possible all day long, every healer has it's own preferences and spell priority
even i deviate a little from the suggested default settings, but then again these are default settings i tested almost 18 hrs in a row, swapped gear to get back to iLevel 455 and tried and tried again to see if these settings would fail in any situation, they did not

a fail came from the whole party or raid, not just me, i did not get OOM with these settings unless there was a general failure and the raid called for a wipe anyhow
to be clear, this is an explanation to all ppl reading this, not just you in person, i can understand your suggestions and settings
these are default settings for a starting holy healer sutable for dungeons and raids with this CR trying to take account for all situations possible, these settings hold up untill atleast iLevel 480 and i beleave it goes further than that
note for you, i did not use food an potions deliberately in the testing fase, not everyone can buy or make them, so i took those out of the equasion, i myself use them, no doubt about that and i do "Melee for Mana" if its needed
Regards