It's harder to try to be the king of that market, as Diablo series has been, arguably, surpassed by other companies. As opposed to Starcraft, which (with Starcraft 2) remains the king of its genre.
If you liked Diablo 2, I suggest checking out Path of Exile in particular, but there's a lot of options there.
(And no, do not mention Total Annihilation or Supreme Commander - they might be better RTS games, but they haven't out-starcrafted Starcraft. They're more strategically oriented while Blizzard still does the fast-paced rock-paper-scissors -style micromanagement RTS way better than the competition.)