It would be great if at any point in time human rights were being severely violated an international power were able to intervene and stop the crises from happening, but this is something that can't happen in the current state of the world. Some parts of the world believe that isolationism is the best way to do things, and feuds may happen if one country were to interfere in the affairs of another. Once these issues are able to be resolved, then it would be correct for an international power to stop a humanitarian crisis.
Humanitarian agencies can often bring many and much more resources to help out and alleviate a domestic problem. From money to medical aid to police and military support, humanitarian agencies add needed services to domestic communities in crisis. Restricting aid to medical, nutrition, and construction/cleanup, the agencies make progress through the crisis faster and with better resolutions. When a domestic community is overwhelmed with aid needs an agency can support the people the domestic community simply has no time or resources to get to all of their people. Agencies bring faster and more comprehensive support as every bit of extra help, helps.