Kodachi is really strong in some raider match-ups but not in others. It's weak good scorcher control in the very early game, which is probably why it's considered weak. A kodachi can at best trade against a scorcher if microed really well, leaving both wrecks in opponents territory.
Kodachi do scale really well vs. most raiders (including scorchers), but they scale really poorly against most other things, so this tends not to be how they are used.
I think these buffs are too far, but that just means they'll be partially reversed later if I'm right.
I'm not sure about the commander changes. Commanders that are morphed are bad, but conditionally okay in big teams where it's difficult to address them with anti-heavy. I don't really know why they're being nerfed further.
Welder buff is crazy. Like... genuinely insane. They're a mini-commander for 220.
Blitz was already good especially vs. raiders. This is a 20% reduction in opposing up-time, for a 10% nerf in damage (assuming you're stunning with every hit which is not always the case).
TB nerf shouldn't change too much, but I like it.
I disagree with GF that BP/cost is the main important attribute of cons. Weight, speed, movement type, survivability, and utility are all important. Conjurer, convict, and constable are among the best cons (before this patch obv.), but none of these stand out for their BP/cost efficiency. If your con comes out earlier with less investment, then arrives at the expansion location faster due to travel time, it doesn't matter that it technically takes longer for them to build the mex. They started earlier.