Gas burn ration is ok for Arma 3. Over all helicopters burn gas pretty fast depending on the engine and tank capacity, weight , crusing alt. I worked on flight operations for a while around Chinoocks, Blackhawks and Kiowas and the range and fuel capacity was always something striking.
Here are some comparison when thinking gas burn rations. This numbers are in the real world. You can take this numbers and you compare the burn ration to each aircraft accordinly in Arma 3. By no mean are they suppose to be exact or close to each other but example is one aircrat range 1000 and the smaller one 250, then you have to assume you make the smaller one burn fuel 3 x faster. Just like in real life. So that is why I would think they burn just as fast in Arma 3
Numbers rounded for real world
Little Bird - 232
Chinook - 1216
Blackhawk - 1380
Wild Cat - 777
Huey - 315
This numbers would indicated that the Little Bird should burn rate faster followed by the Huey so on and so on.