S0u13at3r

Reactors in 1.6.4 need quite a bit of water. Make an aqueous accumulator farm, maybe a dozen or so.

Sorry, no. Just one closed loop between the reactor and turbine along with one stand-alone water input to the reactor. Once you get the system going it really doesn't use that much water from the external water input.

Yes, Fluiducts are limited to 120 mB/T. Are your tesseracts side-adjacent to the ports on the reactor/turbine?

How big is the turbine? Can it accept more than 120 steam?
if it seems to be setup right, but still acts odd, break the turbine and reactor and let them re-form. 
Make sure your reactor is getting enough water too. 

How about reading >this?

1. You have a pregenerated world without Osmium Ore.
2. You add mekanism mod.
3. You enable retrogen (ore regeneration).
4. You now have a world with Osmium.

Retrogen means "retroactive generation", which is a process that takes generated chunks and modifies them to contain the ores.

If you enable retrogen and you restart the server the ores are generating underground.
If you have a base underground some blocks may be converted to ores.
Don't keep any chests with diamonds underground
You will have some lag.

The ores will not be found in any parts of the world that have been already explored, if you added the mod to an already played in world.  Only fixes are to go mining in areas that have never been visited before, or use mystcraft to create an age to mine in.  Since the Mystcraft age will have fresh generation of ores, the new ores will also be genereted normally.
 
there is also the option to use the "retro gen" config option in mekanism and/or thermal expansion.  Thermal expansion one would probably work better.  It would require the server being restarted after the config file is changed.  Drawback to this is the possibility of anything you have underground being replaced by the regenerated ores.  And it can be laggy.  you'd also have to change the config file to turn it off again once the world has been restarted and visited at least once.