I think you have valid points, it's precisely supposed to be "use when usual levels of badass are insufficient", but its limitations arent effective at making that happen.
What is supposed to happen is either:
It's powered and you're a total badass, but it's using power quickly.
It's not powered and you can barely move, your inability to move makes you vulnerable to even weak enemies.
Is the problem you're seeing that it's too easy to keep it powered all the time, you can use it without power, or both?