Not defending either Leonardo nor Tassotti, but what I'll say is that this is no less violent than the other two incidents. With Leonardo, he actually ended Tab Ramos' career. Saying that, it was a wild swinging elbow, not with any intent to fracture his skull (it's just the way it made contact). Here's the video of the incident (one of the worst days in American footy history, as Ramos was one of our most brilliant players).
What I'm trying to get at is that Suarez clearly moved in for the bite, in a very deliberate motion, off the ball. That's unprovoked, violent conduct and it deserves as lengthy a ban if not longer than the Leonardo incident. After all, you don't just send off players if they break someone's leg in a challenge over the ball, but you send them off even if they don't if they come over the ball at all (see Marchisio today).