Roll helm MS damage to vit. Vit rolls really high on helms so the MS damage is less useful because your quiver diminishes it returns. Use Visage of Gunes in your cube. This will work as long as you fix your vengeance.
I don't see enough Cool down reduction. You need 36.33% overall or better for permanent Vengeance. Without this you don't have enough damage or thoughness.
It looks like you have well over 55%CHD. So roll chd off your focus for CDR. Then use the numlock trick to keep it on.
You also need to augment armor.
Your Templar needs attack speed rolled onto his jewelry. You don't care that he does any damage, you care that he procs the ring and neck more often.
You should be able to do at least 75 if you push. Don't get me wrong, you will have to get lucky with pylons, a little. And you have to be aggressive and push past mobs to aggro them and kite back.
If you want to push into the 80s you need augments on all your gear. You also need as much Area Damage as you can get. Without the augments you will not have enough armor or damage. As you have seen things at about 72 one shot you. Once you get half your armor augmented, the won't 1 shot you until you push 76. Full augments at rank 75 should push you onto the 80s. Start by augmenting your gear to at least 72. Then after a couple don't augment below 75. You will have to redo those gems if you do all 70s.