Schlaumayr: I had high hopes for the 1.3 patch, but i still have the same problem: picking the lock leads to the golden cursor stuttering, while I still have 50 fps ... it's practically not possible to pick even the easiest locks with this... so dissapointing :( hopefully with patch 1.4 or 1.5 it will be fixed...
As RoseLegion explained, this is not a bug or implementation issue.
If the "sweet spot" golden cursor starts shaking too much, you are NOT in the actual "sweet spot" when you began rotating the lock. Spend some time to find where the golden point is largest - that's the point you want to keep around.
Higher difficulty chests require greater accuracy (which does mean you have to adjust it as you rotate), but after 1.3 patch lockpicking is hardly difficult. I was able to open Hard and Very Hard chests with 5 skill points (though I'm sure the perk that makes it easier you get along the way helped).
(Very) Easy chests have so much error leeway now you should absolutely have no problems opening them even with clueless level 1 Henry. The inhabitants of Skelitz can attest to it in my playthrough, as things mysteriously disappeared from every but the merchants' Very Hard chests.
I would not hold my breath for any "fix" in the future. Warhorse already addressed the initial difficulty concerns.