1. It's important to realize that WF do not get the proficiency additive PRR bonus from armors. That said, the PRR from armor type is still worth it I think, just not worth as much as if you were not warforged:
http://forums.ddo.com/showthread.php?t=387602
2. You should take overwhelming critical since you already have the qualifying feats. This gives a nice DPS boost.
3. You can do the mitigation calculation like shown here and may find that mithral body with some dodge feats or something could be better:
http://forums.ddo.com/showthread.php?t=383046
My gut feeling on this is no. Dodge gives one of the smallest contributions to damage mitigation unless your PRR is extremely high. However if you were dodge capped through MDB before (since addy body is 1 MDB) then this could give you a huge boost in dodge. That would depend on your choice of gear and destinies and how many extra feats you have to blow on dodge, mobility, spring attack. The other advantage of mithral body is you will be able to have evasion if you take shadowdancer. For defense parameters typical of builds of this type (AC under 100, PRR under 50, not much dodge) it turns out the best investment still tends to be AC, so Adamantine Body gives you the biggest boost there.
I have a 18/2 Fighter Rogue and I went with mithral body and the full line of dodge feats and also combat expertise and bulwark of defense (so I skipped power attack) but it's a stalwart and not a kensei and most people think the toaster evasion tank is 'dead' anyway (if it were ever alive to begin with - people have been saying that ever since I rolled the toon)