The Argrathi's penal technology is incredibly powerful and has considerable potential for positive uses. Get your doctorate in an afternoon! Take a vacation on Risa during your lunch break! If it's any indication of their other inventions, no wonder O'Brien was so interested in their tech.
Ee'Char's incongruous presence in the prison simulation and the irony of O'Brien killing him just days before his release don't seem like accidents. It seems likely that this was all intentionally written into the program as a Batman Gambit to break the victim, which says a lot about the cruelty of the Argrathi.
The properties of the penal technology - compressing years of simulated imprisonment into mere hours - means that there wouldn't be any time to, say, mount any sort of appeal, and we know that they're incredibly quick to convict without any real evidence. How many innocent Argrathi have been put through the exact same thing as O'Brien??
