To avoid oscilloscope ground short, why not simply unground the scope?
That's called "floating the scope".  The problem is the scope chassis is now floating.  If you connect the ground lead to...say...that 220VAC line on your DUT, now your scope chassis is at 220VAC.  You can easily become the path to ground by touching the scope chassis and something else at the same time.

As long as you are very aware of what you're doing, floating the scope can be done.  However, the potential for a mishap is quite high, especially if other engineers come along and don't realize the scope is floating.