No Not at all, Self study is the best study.
But I will suggest to refer any Allen or Aakash materials as these coaching institute do a lot of research work before preparing these materials and they prepare keeping the exam pattern in mind. This will give you competitive advantage.
And most important complete the full syllabus. Often student try different materials/books and syllabus is left incomplete or last few chapters are covered in hurry.
Ps: No need to join class room courses, you can buy materials online as well.
Best would be to join Aakash or Allen Test series. Trust me this will help you a lot