Donning Armour depends on the armour not it's 'type'. So Banded and Splint are Heavy but you don't need help to don them for example
Also to compound on this even though Mithril makes a item one category lighter (Heavy to medium medium to light) doesn't change what the item is. A Mithril full plate would be just as difficult to put on single handedly as a regular full plate trying to reach every little leather strap along the back of your legs sides of your body and back of your neck. Once on though because its lighter it makes it easier to run in jump in.
