Question: If assent is central to faith, does that make deeds unimportant?
Answer: No. The theological definition of faith and the binding importance of obedience are distinct questions. Not identifying a deed with the essence of faith does not mean that the deed lacks religious significance.
Follow-up: What caution is needed when judging a sinful Muslim?
Clarification: Major sins must not be trivialized, but one must not equate every sin with disbelief. Denial of an obligation, treating the forbidden as lawful and committing a sin are different matters.