It's about Ground. The PvP math and design theory junkies are mostly space. Maybe this will improve should Ground PvP become indeed more popular.
But I agree that your observation is interesting and indicates a few issues with the underlying system. (But I think the Grenade global cooldown is a big issue that could serve its own thread!).
In general, the value of skilling for a power - Ground or Space - seems very different and the underlying system is often opaque, requiring lots of testing. Often enough, I feel that the entire game system lacks an underlying structure that could be used to reason about its flaws and advantages and the consequences of changes. Most of it is now is guesswork and experience. But even with that lack - I think it would be good if there was a consistency with the effect of skill values.
I miss a thoroughly designed system like D&D 4...
That's the point. It doesn't feel ok the way it is now and even though it works, there's always something what's called "bitterer Nachgeschmack" in german (leaving a bad taste).
Of course you cannot simply take the values if fully skilled and reduce them by 50% if unskilled, but a bit more of a system would be quite useful for either planning and understanding.