I had a SS/Elec brute and added Defenses really made a difference for him.
Looking over your build, I will say that Power Sink is worth it's weight in gold. And with your end issues, it might be worth working into your build. Energize does good work but PS will just fill you up when you need it.
You might also want to sneak in a kb prot IO somewhere since grounded has a few issues (doesn't work) on slanted ground. I found adding one did the trick for me.
I have a theory for this combo you might want to look at... Originally, it was for a Bio/SS tank (or brute), but that never made it to live. It's a ranged tanker who should take only a little damage.
The key is to utilize taunts -75% range component and then use Leviathan Mastery (+rage). Once the mobs are immob'd and tanked you should not take any more damage.