Former professional player and Team Spirit streamer Ilya "Illidan" Pivtsaev has named the best heroes to raise MMR as position 4. According to his choice, four supports are optimal for this task in patch 7.38c in Dota 2.
Who is better to pick for position 4? Weaver, Lion, Shadow Shaman. Probably Tusk, too. Nothing else comes to mind off the top of my head.
Valve released the letter patch 7.38c on March 28. The developers slightly reworked the map, rebalanced neutral items and multiple heroes. Many outlier characters, such as Abaddon and Dazzle, were nerfed, others were buffed. As always, the changes reshaped the existing meta in matchmaking. More details about meta changes are here.
Earlier, Egor "Nightfall" Grigorenko from Aurora Gaming shared his list of best carries of patch 7.38c. He also thinks there's not much difference between heroes below the top of the ladder and advises MMR grinders to stick to the characters they know well. His three strongest position 1 characters can be found at the link below.