And why would a paper wallet created with respect of best practices be not safe ?
Paper wallet IS safe. But spending it is not. (If you are using "sweep private key" and not an offline signing which is very cumbersome).
Indeed. Yesterday I've send my large stash offline with armoury to my Trezor. Took a lot of time on my raspberry, but I couldn't take the risk of just sweeping the keys at blockchain.info
I only use the Trezor now (and a few mBTC on MyCelium). I've imported the old keys from my QT in a blockchain.info wallet (you never now if you receive a donation from some old image/post/...)