What tank do you like to heal most?

[Ceodore]

...as anyone that's made it that far is at least average at their job...

IDK why I get the feeling it takes a lot to impress you, lol. Generally, a tank who can make it to T9 should hopefully be pretty good. Average generally doesn't make it past T5, and assuming average means the same thing as median, or the middle of the group, then I think you might be forgetting all the thousands of tanks who are reportedly absolutely horrible in the Healing Horror Stories thread, lol. Nah, from my point of view, if you were able to make it to T9 or past, then you are probably doing very well as a tank. Cut them some slack.

...so if you DO look at it this way you'd still be using a lesser Cure to heal the damage over a larger one on PLD...

See, I agreed with you, until you said this. If you're looking at this the way you're saying, it still doesn't actually make sense. The Paladin doesn't take FLAT damage, they take REDUCED damage. There is a huge difference here, and it may be just in the way you worded this statement that I feel like you were mistaken. The healer's heal DOES get boosted on the Warrior, but the Warrior also takes a bigger hit. The healer's heal DOES NOT get boosted on the Paladin, but the paladin takes a smaller hit instead from the same flat damage. I know YOU know the difference. The first is "after the moment" mitigation, the second is "in the moment" mitigation. I also feel you failed, to understand the very fundamental difference in these two. +20% healing is not equal to -20% damage, and I clarified why with numbers and everything here several posts ago. You must realize, while Warriors boost a smaller heal, the Paladin only needs the smaller heal. The only time which a Warrior's buff makes the healer's heal surpass that of the Paladin's mitigation is when the heal itself is already higher than the damage in. Here, check this formula, it's been tested by your handy dandy local math and physics nerd...
For Paladin: Y=(4000-(X-(X*.2)))+Z
Where Y is health, X is damage in, and Z is Healing in.
For Warrior: Y=((4000*.25)-X)+(Z+(Z*.2))
Where Y is health, X is damage in, and Z is healing in. Both tanks have a base HP of 4000. Also, be sure to use PEMDAS.
Both scenarios assume precisely identical tanks with no other modifiers, CDs, or RNG and show that at their core the Paladin is the easier of the two. Healing increase IS NOT equivalent to damage mitigation. IDK how much clearer I can be with my numbers, the math doesn't lie. These scenarios show that with the exact same heal, the Paladin actually recovers a larger % of the HP lost than the warrior does, in fact, even a larger % of their total HP too. Go ahead, do the math. Better yet, allow me to do the math.
Allow me to show a scenario. Assume damage in is 1000, and assume healing in 999, just 1 less than the damage coming in. I will show you why I stated that the difference is only when healing in is greater than damage in does the Warrior's healing boost surpass the Paladin damage reduction.
Paladin
Y=(4000-(1000-(1000*.2)))+999
Y=4199 coming to 199 over healing
Warrior
Y=((4000*.25)-1000)+(999+(999*.2))
Y=5198.8 coming to 198.8 over healing on the Warrior's 5000 HP pool.
Now, to show you when the Warrior healing buff is better... when healing is greater than damage in. Assume damage in 1000 and healing in is 1001.
Paladin
Y=(4000-(1000-(1000*.2)))+1001
Y=4201 coming to 201 over healing
Warrior
Y=((4000*.25)-1000)+(1001+(1001*.2))
Y=5201.2 coming to 201.2 over healing on the Warrior's 5000 HP pool.
I AM aware that there are no decimal places in this game, and that in the first scenario, it would be just a flat 199 over heal for Paladin to a 198 over heal for Warrior and in the second scenario the over healing would be the same. I simply wished to demonstrated the point mathematically at the exact point where the trends of the buffs change and in what way. This illustrates that when the base damage in is greater than the base healing in, the Paladin's buff is better, and that when the base damage in is less than the base healing in, the Warrior's is better. This does not, in now way make either unviable, it simply illustrates that the healing requirement on a Paladin at its core IS slightly less than that of a Warrior in order to keep the HP pool full. In fact, allow me to demonstrate at what point the heal have no over heal and still restore the mitigated damage on a Paladin but not restore the Warrior back to full even with the boost in healing. in the scenario where damage in is a base 1000, The magic number in this situation is 800 base healing in.
Paladin
Y=(4000-(1000-(1000*.2)))+800
Y=4000 No over heal at all, but back to full HP.
Warrior
Y=((4000*.25)-1000)+(800+(800*.2))
Y= 4960 A net loss of 40 HP from the Warrior's 5000 HP pool.
This demonstrates the same base heal in against the same base damage in for both tanks with only the difference being in their toggle buffs, nothing else.
I'm going to tackle another point that's probably going to come up. % loss of your HP pool from base damage in. This is probably better known as spike damage, the visual appearance of how much damage from an HP pool is taken away from a certain amount of damage. For this exercise, we are ignoring healing entirely, we are assuming that both tanks are simply standing and just absorbing damage. The factors that come into play here are the Warrior's +25% HP increase and the Paladin's -20% damage reduction and only variable is the base damage in. So, let's assume two decent ilvl tanks with a base HP of 8000.
The Paladin has the flat 8000 HP, the Warrior has an increased HP of 10000 (8000 + 2000, which is 25% of 8000)
Scenario 1
Both tanks take a hit worth 2000 HP first. Y is amount of HP left.
For Paladin
Y=8000-(2000-(2000*.2))
Y=6400
Y%=6400/8000
Y%=80% of HP pool left
For Warrior
Y=10000-2000
Y=8000
Y%=80% of HP pool left
To make sure that this trend is not just a magic number of 2000, let's change the damage in to 1000.
Y=8000-(1000-(1000*.2))
Y=7200
Y%=7200/8000
Y%=90% of HP pool left
For Warrior
Y=10000-1000
Y=9000
Y%=90% of HP pool left
Let's go the other direction, increase damage in to 3000.
Y=8000-(3000-(3000*.2))
Y=5600
Y%=5600/8000
Y%=70% of HP pool left
For Warrior
Y=10000-3000
Y=7000
Y%=70% of HP pool left
So neither tank actually takes more visual spike damage actually as this trend continues in equal in both directions.

**TL;DR** The above crap doesn't matter anyways, play what you want, cause it's all about da skillz...

Also, nerd alert...

Edit: For size purposes, I've reduced text and removed enter spaces, this really is too much, I know, but I'd like to bury this.