Sayyed Mohammad Al-Musawi, Sayyed Mohammad al-Musawi is originally from Iraq and heads up the World Ahlul Bayt Islamic League in London. Other than being involved in various humanitarian projects, he frequently responds to... Answer updated 2 years ago

Most prominent scholars among the students of Ayatullah Sistani or any other Marja' of Taqleed are not announced in public and it depends on the opinions of different leading scholars who evaluate those students and judge who are the most senior among them. 

It might be more suitable to send this question to the office of Ayatullah Sistani or and see whether they find it appropriate to reply.