Well it seems that the spire debuff apply to the healing skill, although that skill it is fixed and not influenced by any kind of stat, it seems that the devs of the Icarus considered that the spire will break this and well 5% -10% heal max charge and who knows how much at min charge (probably 2-3%).
This is the official answer:
Greetings Rider,
Thank you for contacting Nexon America Customer Support.
I understand that you are having issues with your heal skill inside Ellora's Spire. First of all thank you for the screenshot that you have provided. The reason why you are healing for a lesser is because of the Spire Challenge debuff which varies depending on the class. If you notice on your screenshot, there is a scroll icon below your buff icons. Please hover your mouse on that icon and it should show you the debuff details.
Let me know if you need further assistance and I apologize for the inconvenience this may have caused you.
Should you have any other concern, please don't hesitate to submit a new ticket or contact our Chat Support: https://support.nexon.net/hc/en-us. You can also visit our website for news, updates and events.
Sincerely,
GM Elmwar
Nexon America Inc
==========
Well lvl 50 nothing to do, many bugs, not really worth my time, someone complained that assassins get shafted well I also believe that priest got shafted also, I see no other class with nerfed skills in the spire.
This is the official answer:
Greetings Rider,
Thank you for contacting Nexon America Customer Support.
I understand that you are having issues with your heal skill inside Ellora's Spire. First of all thank you for the screenshot that you have provided. The reason why you are healing for a lesser is because of the Spire Challenge debuff which varies depending on the class. If you notice on your screenshot, there is a scroll icon below your buff icons. Please hover your mouse on that icon and it should show you the debuff details.
Let me know if you need further assistance and I apologize for the inconvenience this may have caused you.
Should you have any other concern, please don't hesitate to submit a new ticket or contact our Chat Support: https://support.nexon.net/hc/en-us. You can also visit our website for news, updates and events.
Sincerely,
GM Elmwar
Nexon America Inc
==========
Well lvl 50 nothing to do, many bugs, not really worth my time, someone complained that assassins get shafted well I also believe that priest got shafted also, I see no other class with nerfed skills in the spire.