Language is crucial for almost every domain -especially Law. How reliable can a legal professional be without a background/competence in linguistics?

Being a legal professional, language is highly important as it serves to communicate and to understand. If a legal professional cannot fluently express himself, his clients might feel a sense of discouragement in the compentency of the legal professional. If legal professionals lack communication skills, they shall obligatory take a language course and ensure that they pass the test.

Very competent.  While most legislation and case dispensation is written, legal professionals engage in additional tactics for the bulk of their work.  

Over emphasis on side-speak, dense vague pitfalls, and excessive technicalities are base antics used to flesh out issues.  Successful lawyers and firms do not rely heavily on banal technicalities at every turn.  

Prudence  in gauging relevance, contextual appropriateness, and the financial burden/outcome goal parity are all decisive factors in legal professionalism.