change your offhand weapon.
the dps doesn't matter.
tornado and rend damage are based on main hand weapon damage, only your ww damage also factors your offhand damage, but thats not your main source of damage.
get a weapon with socket, critical hit damage, life steal, strength. preferable a spear with increased attack speed.
2nd solution for an offhand weapon would be echoing fury but then you must decide between critical hit damage and life steal.
Further you can upgrade your mainhand weapon. If you don't use echoing fury in offhand, you can get it in mainhand, but it should have low fear chance. With higher fear chance I don't would use it in mainhand and buy another mainhand only with high dps, socket and cricitcal hit damage.
If you upgrade your weapons, take a look at tornado breakpoints.
if you won't upgrade your weapons, then I would upgrade your gems. Upgrading your gear is very difficult, because it will cost more then 100 mio to get a really upgrade.
You could gain at least another 100 str by switching out those Blackthorne's pants for rare pants with 150 str / 150 vit / 60 resists / 2 sockets. Don't know about US, but these are around 30mil on EU AH. You'll need to work out the impact of losing the 11% life if you do this.
If you replace your wep as suggested above with life steal you wont need the LoH on the Blackthorne's anyway.