This is similar to my issue now. I need to upgrade one piece of armour to get 1 more light then I'll hit level 28 and hopefully be able to solo the weekly heroic and join a team for the raid. There will be no point upgrading my armour further unless I get raid armour and since I'm behind the curve, as soon as I do that it'll be time to do the new raid and scrap my armour again! Frustrating.