i thikn she's okay. i think her gambling problem is there to give some comedy to her character. such as jiraiya's pervy-ness. i dont think its all that serious. and i dont think you're really fair there with the deaths. okay a doctor should learn to handle deaths but both her boyfriend and little brother died in her arms. personally i would of course want to see jiraiya as hokage instead of tsunade but she was the best alternative. and besides jiraiya is still there to give advice if needed. so its not all that bad. and she is one of the sannin you would think that she can be serious if its needed.