Don't bother with death sentry unless you plan on being some type of hybrid where you would max both death sentry and lightning sentry. The damage with only one or a few points in one or the other is too little damage. As zupp already said, dumping a good chunk of points into shadow master will give you a good tank to rely on.
If you decide to remake, another suggestion is to choose either physical or elemental and not mix them. There are too many skills and stats for a physical/elemental hybrid assassin to sync into effectively. That would clear up claw mastery, for instance, and get your primary or secondary element going rather well. Then you're also not worrying about lacking crushing blow, open wounds, etc. and can focus on elemental damage and +skills.
I hope you remake. Marital art assassins are fun!
