Well...
The only time I've ever done much welding on an intentionally grounded task was building a shop a bunch of years ago. The structure in question was a framework to be poured into the slab and I was welding a steel curb into it after the walls were up and the frame itself was finished and bonded to 4 grounding rods.
When I started welding in the curb, I found that the welder seemed to be putting out a lot less power than expected. I checked the settings repeatedly and couldn't figure out what was wrong. After arguing with it for an hour, I decided to do some testing. I set up some scrap (of the same material) on the bench and tried welding it there. By this time I had cranked the machine up to 225 amps (max). The arc was incredible.
My conclusion at the time was that I was doing something wrong. Then a friend pointed out that the only difference with the framework was the ground connections.
We pulled the ground connections while I finished the curb and I went back to the 120 amps I had been using all along and there were no problems.