What you've missed is that the Shifty power doesn't do any of this on it's own. Hey look... Power Attack in Pathfinder makes your attack directly more powerful (causes more damage), at a reduced chance to hit. That is a mechanic backing fluff... the attack is actually more powerful in damage than a regular attack. Shifty in and of itself allows you to shift 5 feet as a 5' move, and generates none of the supposed fluff people want to attribute to it. Nothing about it is sneaky, deceptive, or involves trickery.
Shifty demonstrably makes Kobolds slippery little buggers. It means they can move when and where other people can't. It doesn't make them deceitful (although actually it does make them better at ducking into cover and hiding - they can use their minor to either poke their heads out to prepare to attack or to dart back into cover). It makes them slippery and hard to lay your hands on. Which helps any trickery they want to do that involves moving.
In terms of mechanics and fluff, Power Attack is, by contrast, barely visible. In order for
anyone except the wielder to notice a power attack it needs to explicitely be called out. And would barely be noticed in character at all. The average power attack has an effect that's barely distinguishable from a normal blow. You'll still end up in the normal range most of the time. Shifty, on the other hand, you
see on the tabletop. It's much more visceral. It's not in the normal range of things (unlike PA). A better comparison to Shifty would be Spring Attack.
In terms of mechanics supporting fluff, putting Power Attack up against Shifty is the equivalent of entering an arse kicking contest with a centipede the same size you are.
An RPG which apes MMORPGs and M:tG for design direction. D&D is better and more "D&D" when it draws upon an important wargaming habit: attempting some sort of simulation of the topic at hand. Thus your RPG is arguably a regression from something done better decades ago.
When D&D tries to go fully simulationist it becomes a clarinetist; it simultaneously sucks and blows. Have you ever looked at the D&D economy? As your rant about epic wizards illustrates, D&D does not simulate its source material (it has epic wizards but not epic fighters and the wizards get to overpower everything). 4e on the other hand is great at simulating both pulp action and mid-power mythology; the fighters can't cut the tops of mountains - but the wizards aren't epic either. Fafhrd and the Grey Mouser work well in 4e (Mouser just needs a ritual caster feat) and can go on for quite a while. It doesn't do grit - but the
genres it simulates aren't gritty either. The whole thing runs on Holywood Physics (which might include Michael Bay movies, but also includes Raiders of the Lost Ark, Die Hard, and the 13th Warrior - and I really wouldn't bet against Holywood using square fireballs). Classic D&D on the other hand tries to simulate the real world. Except where it doesn't, and where the whole thing collapses.