Brock, the former managing director of Tribal DDB, and Dyke, the former head of planning at DDB London, have already hired the Diageo media manager, Leo Moore, and Deidre McGlashan, the head of global client management at Isobar, as partners.
I-level has no plans to replace Ling, who was the agency's first employee after its launch by the founders Andrew Walmsley and Charlie Dobres in 1999.
It recently appointed Jamie Kenny from Miles Calcraft Briginshaw Duffy as the head of account management, and OMD's Matthew White as the head of planning.
Ling's departure coincides with i-level holding talks over a potential acquisition with companies such as Aegis Media and AKQA.
Ling was unavailable for comment.