I just experienced two mutinies in my 4-player game against the AI as Austria-Hungary that gave me the impression that these events can be overpowered. The game was still in early 1915, progress was good and all fronts were well secured with troops at full strength, recruit points were at maximum and morale around 40. Then Russia played a mutinies event that ravaged my troops, with some armies receiving up to 7 (!) losses. Recruit points were set to zero, and only a handful of units could be refilled with newly arrived recruit points. Then on the next turn Russia again played a mutinies event, leaving many armies and detachments as empty shells without troops and again setting recruit points to zero. So practically in two turns without any major combat my situation went from perfect to hopeless.
This was certainly bad luck but I ask myself whether randomly drawn events should be that decisive in determining the outcome of the game (and able to end a balanced game in such an early phase). Maybe mutinies could be somehow linked to the national morale (high morale makes mutinies less likely to succeed or prevents some of the losses).