I think it's like you play Rhino-Abzan or you play Jund. Run a Painful Truths main with a few in the sideboard for grindier match ups. Lingering Souls also lets you keep making plays when you've run out of cards. Siege Rhino is a amazing top deck and will win you games where as Bob is a mediocre top deck that'll maybe help you keep up. Also, as another commenter noted, with out Bob you can play Tasigur and get card advantage that way as well.

(BTW Dromoka's Command seems kind of lackluster is your list but Siege Rhino makes it way better.)