Think you still have to have the classes unlocked first. Just have to either craft or find the base armor for a class to play it, then use the drakeskin. I try not to use any kind of cotton, everite, craggy skin, great bear hide when crafting armors(I save those for weapon upgrades). the materials you put in the armors when crafting them in mp are irrelevant, the stats will be the same whether you use all tier 3 materials or all tier 1 materials. So trash mats are really good for class unlocking/armor crafting.
That's what i gathered so far.
Can you tell me what gives you cotton? I have salvaged hundreds of gear and have yet to obtain even one.