Did you pick 250 CE for any particular reason? The "Crisis of the Third Century" makes this an interesting question, if only because Decius' rule ends in 251 and then it's a revolving door of emperors and claimants until Aurelian. So, in that respect, depending on when/where your criticized the Empire, there might not even be a recognizable head of state (or, at the very least, a stable one).

It also depends who you are. You say "academic," but that could mean anything. Alexandrians consider themselves "Romans" at this point, and wouldn't necessarily see themselves as outside the apparatus of Empire or the imperial project. They wouldn't have understood dictatorial rule in the way you mean it. Now, if you were a Hellenized Jewish academic, things might be different. There are lots of critiques of Roman imperialism in Jewish writings -- but even in their most apocalyptic forms, they're still pretty vague about the sitting emperor.

To write against the Emperor was, in the Late Antique period (which could technically include 250 CE, depending on how you define it) a case of maiestas, or treason. Even earlier, Tacitus couches criticisms of Domitian in his biography/eulogy to his father in law, Agricola. Following Tacitus' lead, it seems to be the preference of historians/academics to write about past emperors "sine ira et studio" (without anger or enthusiasm) because they were able to be more objective. Many historians have attempted to read dissatisfaction with contemporary emperors or power apparatuses in the critiques leveled at past emperors.