Yes, dangerous offender laws in Canada are adequate, because they do a good job of punishing repeat offenders, and making sure that people who are likely to commit crime are monitored, and in some cases committed. Crime rates in Canada are relatively low, although that is likely because the drug trade is not as far into Canada as it is to the United States. Even so, legislators have done the right thing by balancing freedom with Canada's dangerous offender laws.
Regardless of the sentence dealt, in Canada, a dangerous offender may be held for an indefinite period of time if they are deemed to be a threat to society. This is adequate because violent tendencies are dangerous. If one was released and committed a violent act, all would ask why the individual did not remain detained. The dangerous offender laws in Canada are adequate.