Why is it useless? Being able to obliterate four blocks deep of stone in a single shot makes hollowing out building areas a whole lot faster than using the diamond drill. It also makes long-distance tunnelling a whole lot faster for the same reason.
For all of the 10 seconds of battery life you'll get in that mode. Seriously, I'd be better off just lugging another diamond drill or batpack around instead, most of the time.
I think it really needs to be able to draw power from a batpack - and that we need a Tier 2 batpack that can supply such things. As it stands, 64 uses is about what you'd get out of a wooden pickaxe. Sure it's more powerful, but its uses are so limited (in its primary and practical mode) that one is better off with another tool.