I cannot emphasize enough how important 2FA is ensuring your funds is safe. Just because bitcoin offer security does not mean it is as secure as the fort knox. It has chinks in the armor and cracks in its shield that experienced hackers can take advantage of and sabotage, so it's better to take care of your money like it's your child, or the child of your friend you were asked to carry for a while.
After reading the OP comment I didn't quite understand how he was robbed! I am playing on Bitsler for some time, and I didn't have any problems with my deposits or withdraws. This is probably a special case, malwalre or pishing site, who knows, but it's not the reason to badmouth a casino becuse of it!
2FA is for protection, and when you have additional protection it's always better! I never had problems with 2FA, and I recommend it to people I know, so this topic concerns me a bit... I think that OP did something wrong, but he is not aware of it! He will have to rethink his steps!
Prolly not from Bitsler but somewhere along the path of transaction, Bitsler is secured, but then again we cannot really say for certain what happened. Let this just become a costly lesson to OP to use 2FA next time.