Ra's was, yes, by getting on that train by himself and destroying the train when running straight into Gotham Tower, but the League as a whole weren't on a suicide mission. They were to make sure Gotham builds itself back up to start all over and so too the LoS would start over, but the entire League were never as suicidal as shown in TDKR; in BB, it was only the leader. In TDKR, we see members sacrificing themselves, we see Talia planning on sacrificing herself. Or, unless he wants to accomplish something the famed Ra's al Ghul couldn't achieve. Yup, I'll choose door number two since I never viewed Bane as a lovesick puppy.