Is a ninja class needed in RPG maps?

If a ninja is only needed for their abilities, then I don't think so (he won't be the only one in the group, so his skill won't work. Or what skill does he have? I don't remember.). If he's needed for the plot and his skill doesn't matter, then you can leave him.

There will be 4 (or 6, I'll decide later) heroes in the group, not just one warrior, so he won't be a hindrance in any case.
Besides, he can be sent to wander the map alone.)
He's not essential to the plot, but... I haven't decided yet.)

Added 5 minutes later
SKILL: The Ninja attacks and at the same time attacks with poison.