Lowbie WAR threat weapon question

[TheFishyOne]

'ey guys.

Right now, my 19 WAR is tanking with a Jarsath Trident in MH, and a Green Jade Broadsword in OH. They produce enough aggro to meet my needs for now, but 20 is almost upon me, and with it, the removal of dmg caps. I have been considering swapping my trident with an Obsidian Shard I have in my bank, but my DEX is only 110 w/o trident, and I'm lucky to have it proc once every minute. I'm also broke as a joke for the time being, so I guess my question to you guys is:

• How much DEX should I have to make Obsidian Shard worth using, come 20?
• Around what level will I need to have this in place to remain viable as a tank?

Many thanks in advane for any input you guys have.