Simple answer:
NOPE
Site could be easily hacked.
But if I use 2F authentication? Is safest or not?
There is nothing safe even with 2fa you could still be hacked. If you are really looking to store your btc for over 10 btc then use a cold wallet instead unless you are planning to regularly spend that 10 btc back and forth then use hot wallet instead but obviously dont use blockchain.info but rather a desktop wallet