The reason why you will only see about 400 mW out of a "corrected" laser is the easy way to correct is to mask off 2/3rds of the beam and only use the central spot. It has nothing to do with coatings or lens materials, its just simple physics, and production costs.
If you use anamorphic lensing (prisms, cylinder) it requires a huge amount of space, lots of custom glass, extra machining, and each laser needs hand adjusting to match the diode, which no manufacturer is willing to pay for. Remember pointer makers are just in it to make a buck, they do not share your enthusiasm for lasers. They are not going to pay some one to do two precision gluing steps (lens epoxy needs 40 minutes) 45 minutes apart when plenty of people will settle for 400 mW.
Masking allows them to fit the whole mess in a existing body, reducing costs.
You are now seeing the tradeoffs between desire, laws of physics, and production costs.
Steve