Those weren't dictatorships, given that that word has concrete meaning during the Roman Republic. The actual dictatorships were those of Sulla and Caesar, and neither dictatorship was elected by the tribes.

Also, very much true. Original poster talked about ostracization in anient Athens, but assigned it to Rome.

I'd point out that your comment reads like an optimate framing of the tribunates of the Gracchi brothers - I know that they gained unconstitutional multiple terms in a row, but as far as I know their popularity was genuine, not requiring what sounds exactly like the complaint of an oligarch about the riff-raff.