My assessment was also in March, and I am in exactly the same position as yourself.
13 weeks ago since I submitted my MR and when I rang up I was advised the DM had applied to ATOS for more information on the Assessor's report. I was advised ATOS had sent a response and now the DM had all of the information now to make a decision on the MR.
2 weeks later I am still waiting. Have you heard anything?