Even with later start dates they're a pain. You can leave em' with just Egypt and they're still a stable realm with access to a merc group that's the size of a medium kingdom's total army by itself, and a holy order that gameplay-wise exists solely for their benefit. They absolutely need a re-balancing... the potential for them to become a nightmare should exist, but I truly get sick of watching them, game after game, just ROFLstomping everything in sight... the only times I've ever seen them not turn into some ungodly blob is when I've focused my entire efforts into stopping them, and even then it requires a massive amount of luck. One time, when I was the emperor of Persia, I'd helped reduce them to a single county.
Within a decade, they'd taken Greece from the ERE.