Speaking for myself I have no use for those curing artifacts except to sell them and raise more silver.  Every video I ever saw on artifacts puts those in the junk category.

As far as your question,

Curing (4):

Increases value of Healing done by the Champion by 20%. It’s important to note that this set only applies to Healing the Champion casts. Meaning it does not stack with Artifact Sets such as Lifesteal or similar effects. 

My  research  has  lead  me  to  believe the  Curing  Set  is  utter  trash.

It  only  applies to  out  going  heals  which  have  been  casted  by  a  healer.

It  doesn't apply  to  Continuous  Heal  Buffs.

It  doesn't apply  to  Artifact  Sets.

In  addition,  my  research  has  discovered,  The  Curing  set  is  only  good  on  healers  who  heal  based  on  Allies  Max  Health.

2  Types  of  Healers  in  game

1.  Heals  based  on  Their  Max  HP

2.  Heals  based  on  Allies  Max  HP

Healers  which  heal  based  on  "Their"  Max  HP  heal  more  based  on   Total  HP.

The  more  HP  you  stack  on  them  -  the  bigger  the  heal

Curing  set  does  20%  Bonus  Heal.

The  problem  is  it  is  a  4  piece  set.

It  takes  up  4  gear  slots.

You  could  use  those  4  gear  slots  for  like  Immortal Gear.

-  2  pieces  of  Immortal  give  you  15%  more  Total  Health.

-  4  pieces  of  Immortal  give  you  30%  more  Total  Health.

A  hero  who  does  more  healing  based  on  "Their"  total  HP  misses  out  on  30%  extra  HP.

Again,  your  hero  can  only  wear  6  pieces  of  gear.

6  Immortal  or  4  Curing  +  2  Immortal

6  Immortal  =  45%  more  Total  Health

4  Curing  +  2  Immortal  =  15%  more  Total  Health  +  20%  Bonus  Heal

The  difference  is  30%  less  Total  Health  vs.  20%  Bonus  Heal.

Lets  say  hero  based  HP  is  20k

Lets  say  hero  wears  6  Immortal  which  give  them  29k  Total  HP

They Heal  10%  of  Total  HP which  is  29k  =  2,900  Heal

Lets  say  hero  base  HP  is  20k

Lets  say  hero  wears  4  Curing  +  2  Immortal  which  gives  them  23k  Total  HP

They  Heal  12%  of  Total  HP  which  is  23k  =  2,760  Heal

How  did  we  get  12%  Heal?

The  Bonus  Heal  is  multiplied  by  the  regular  heal  --> Then  added  to  make  total  heal.

10%  Normal  Heal  times  20%  Bonus  Heal  =  2%

The  Total  Heal  with  Curing  Set  on  will  be  12%

(10%  from  Normal  Heal  +  2%  from  Curing  Bonus  Heal)

You  can  start  to  see  why  Curing  Set  is  better  on  Healers  who  heal  based  on  "Allies"  HP.

The  Curing  Set  Heal  doesn't  make  up  for  the  sacrifice in  Total  HP  loss.

Again  if  I  made  a  mistake  -  People are  more  than  welcome  to  correct  me.

I  am  under  the  impression this  is  how  the  Curing  Set  Functions.

If  it  does  function  like  this,  The  Curing  Set  is  pretty  bad.

It's  Bad  becuase  it  only  applies  to  a  select  few  healers  in  the  game.

It's  Bad  because  the  Bonus  Heal  isn't  a  huge  factor.

For  Example:

Sycl  of  Drakes  Heals  based  on  "Allies"  Total  HP.

Would  you  put  Curing  Set  on  Sycl  of  Drakes?

I  doubt  anyone  would  do  it.

They  would  probably go  Relentless or  Speed  to  help  her  take  more  turns  to  heal.

Do  you  see  what  I  mean?

Even  when  hero  meets  the  criteria to  be  a  Curing  Set  Wear,  It  still  seems  like  Bad  Idea  to  put  Curing  Set  on  them.

I  hope  the  game  Buffs  Curing  Set.

It  needs  help.

ok well then maby it will be good for the Frostkin + Ironclad combo due to frostkins deaplet turnmeter that turns to heal and ironclads passive that hits from surplus heals 

Curing Set ,, ONLY GOOD for a Supply of Silver ,,,,,,, 

Completely useless except to sell for silver

I  don't know  how  Frostkin  Heal  scales.

It  says  turn  meter,  but  its  not  very  clear.

I  guess  the  only  way  to  know  would  be  to  test  it.

Try  Frostkin  in  Curing  set.

Try  Frostkin  with  out  Curing  Set.

Everything Player J has said above is correct.  I tested the Curing set quite extensively in the past to see if it was any use and the bonus to heal only impacts the amount being healed

For example, assuming a character has 20,000 HP, and heals for 10% each round.  Normally they would heal for 2000 HP.  With the curing set, this becomes 2400 HP, as the 20% bonus to heal is based on the value being healed.

In other words, it won't take a skill that heals 10% and make it heal 30%

Ultimately, I find the set to be virtually worthless

I havent tried it out myself yet (And I really should, looks like fun), but all the iterations of the Frostskin + Ironclad + Cardinal teams I have seen DID have their Frostskin in a curing set.

Which, I agree with you, is one of the few (if not the only) places where the curing set has any merit.