They could keep the steps the way you are, but just make the steps require achievements instead of task completion. This way if you got achievements for the various bits ahead of time, when you get to that step of the attunement you just need to get whatever achievements you have left. Obviously they would need to add achievements for whatever tasks currently don't have them, but otherwise it seems like this approach would be easy.

I like that it is a long process though, it means guilds have to help players get it done if they want more raiders. It used to be like that in WoW when they had 40 mans. It was hard to fill your roster so guilds had to work together and help new recruits to get it done. This had a pretty big positive impact on the community IMHO. When it started becoming easy to replace people relationships became a lot more disposable in WoW.