Sorry for bringing out this topic from so long ago.
This question (you can change your encoding to Chinese Simplified by changing Browser settings) asks - "In order to understand our mind and realise our Buddha Nature, is Karmic Cleansing required"?
My answer is Yes... because people with low capacities, karmas will obstruct them from liberation. Even in Zen traditions methods of karmic cleansing are practised... so it's not really only confined to the Vajrayana.
But once the person sees his Buddha Nature, that where the real work of Buddhism begins.
Just like after you realise the bright shining nature of the mirror, you will wipe the rest of the dust away to reveal the mirror perfectly. Thus perfecting Buddhahood.
Wiping the dust is likened to cleansing of the 8th Consciousness, or the Alaya Consciousness (the storehouse for karmic seeds.. and also where memories are kept).
However to the enlightened Karma no longer obstructs them. Karmic effects arise and ceases itself... the mind does not become affected.