Going to split this from Fenier's data thread (http://eq.forums.thedruidsgrove.org/showthread.php?t=12644) to keep it clean. If you've been using ATK debuffs more frequently having read that post, please share your experiences here. This is mine:

I am modestly geared compared to many posters on these forums, and I have less than 100 AA. Last night I was in Last Migration (Hard) backup healing and debuffing. I used: Hand of Ro, Sun's Corona, and Fixation of Ro, and for me, even with a small-ish mana pool, I felt signifigantly more comfortable in situations where I had to main heal. Mana became less of an issue because the mobs simply were not hitting for their maximum as frequently.

I do not crit heal very often yet, and so being able to debuff mobs to the point of SI doing something other than simply negating the damage my tank was taking, made my job much easier.

There really is something to this, I think everybody should try it next time they are healing for a group and feel uneasy about it. It made all the difference for me last night.

In situtations where I'm not the primary healer, I'll stick Hand on Ro on pretty much every mob that comes to camp. I seriously dislike when my nukes are resisted, so I reduce the likelihood of that happening, and obviously the debuffs speed the kills and reduce the healing along the way.

In situtations where I am the primary or only healer, the debuffs are tailored to the situation. I'd -like- to apply debuffs on everything, but honestly when some mob is taking the tanks head off and inflicting heavy damage, I'll slide debuffs in as I feel secure, but I'm not likely to remove the tank from my target to make the debuff any sort of priority.

I am the only healer in most of my exp groups.

Depending on how good at aggro your tank is, you can land Hand of Ro on incoming and follow up with Sun's after the mob is slowed.

There are some mobs which hit hard enough this is not possiable, however in most cases it should be. Worse case you can always mez the mob (assuming the group can mez the mob, and the mob is mezzable) and debuff it prior to engague.

While the second way is slighty more time consuming, it would still lower your downtime drasmtically.

-Fenier

I play two roles that relate to this, so I will share both points of view.

On my pally, I can tell the moment the second debuff lands. Usually I am being torn arpart at the seams (especially in missions like the one Juniper mentioned.) Then Sun's Corona lands and wow... The debuffs drastically change the amount of damage I am taking. It reduces the overall amount of heals I need to stay alive and makes me more secure in being able to tank the area I am in.

On my druid, I have played main healer a few times in groups. I have a whopping 15 aa... and 6500 mana buffed. I have main healed MPG, DoNs, and a couple DoDs with a 9.5 - 10k ish tank. The debuffs drastically reduce the downtime our groups suffer due to me being low on mana. They make it where I can use my cheals over my fast heals. I honestly rarely ever de-mem them.

--Nae aka Sabby

I started using the debuffs when I read Fenier's post and although I have no hard information, I can tell you that I have noticed a huge difference in the amount of heals needed.

Just yesterday I was doing a Creator mission with me as the only healer and I was able to get the mobs debuffed before getting the tank healed. I usually only had to heal him once per fight. I am glad that Fenier has given me this relevation!

I have always used Corona and Hand religiously (Well, since Avendesoral told me too a long time ago) and have been preaching them to anyone who will listen, but had no idea that we had a third that stacked. I didn't even have Fixation of Ro in my spell book, but I found it in Bazaar for 32pp. Very awesome.

I'll copy this over from the stickied thread:

A bit of background before I'll put in my chips on the value of these:
I live with my girlfriend, and one of my coworkers and his girlfriend. We all play EQ in the same room, and have a pretty solid group, and handle on what we can/can't do with our group (War, Cler, Dru, Mnk, Enc), and recently my gf's brother joined up with us, as a newly 70 shm (bit of overlap between him + my chanter).

We recently tried to do the 69.2 hard run to get the belt for the warrior (significant upgrade). Our first couple pulls were standard tash/slow/hand of ro... and it was brutal. Cleric had to spam smaller heals, with the druid helping, because CH + spots weren't enough. We had a couple deaths, some med breaks, and it was just generally slow and painful.

We decided we'd try pulling a single, mez it, do the 3 druid atk debuffs (sun's corona, hand of ro, fixation of ro) as well as synapse spasm and weakness from the chanter (didnt want to put asphixiate on, in case we had to re-mez), and a slow, of course.

Mez would drop... and the cleric was able to lazilly use only CH, without ever needing a spot heal.

This became our Standard for the mission. No more deaths (well, chanter once when warrior was distracted, and chanter got a resist on mez), and it was easy, smooth sailing after that. It added about 30 seconds to each mob, but it was a heck of a lot less downtime than med breaks + rez breaks that we had to face prior to that.

I havent had a chance to measure how much the 3 strength debuffs from the chanter have on hit distribution, but I'm assuming that they have a similar effect based on how strength affects ATK. Someday I'll get around to testing that :P