I think you've missed the point of the thread - to examine how a bead fails, not to make a structural connection. There's no way I'd use that weld for any kind of application.
I used those thick sections partly because they were at hand, and also because they may have revealed insufficient fusion to the base metal, something pretty common with MIG welds without enough heat.
For actual connections of that thickness of steel, I bevel one or both parts, do a root pass with the MIG then fill up the join with multiple passes of stick - if it's flat position, Ferrocraft 22 is a bit of a favourite.