Power is essentially meaningless unless it's super low or *super* high.

It gives, imo, far too much weighted value to hp and resistance, and no where near enough to speed and crit damage.

So let's say you see a nuker like Thor, and he's got 80k power. (note: I'm making up numbers here, they're ballpark at best)

Maybe he's got 60k hp, 400+ res, and can't hit worth a damn.

Or maybe hes got 25k hp, 100 res, but he's got 400 speed and 400 crit dam.

There's no way to tell unless you see him in action.

Tl;dr - nothing.

Power level doesn't always reflect strategy, focus on tactics, not numbers. 

Power level overvalues HP and res, and undervalues speed and crit dam.

Ninja is typically best built as a glass cannon: all damage and speed. Which means he'll likely have a considerably lower power level than, for instance, Rhazin, a high res, tanky, slow champ, even though Ninja is considerably stronger

that's gotta be a redditrap

The Classic Arena is very annoying.  One guy with a 1/4 of my power level can take out all four of my characters.  Something is amidst.

yep, you called it, edited in extremely suspicious link

I'm assuming you're talking about Armanz but regardless of who it is, it's a teachable moment. Don't always go for the 1 man defense teams (or a UDK with 3 commons) depending on who the champion is. Sometimes it's a trap and other times it's a Paragon that has super high resist, youll only have a 3% chance to remove their unkillable (unless they're REALLY trolling and use Protection Set) so you'll waste 5-10 minutes till you quit. 

There were a few solo champs I really hated in arena when I first started playing, Wythir and Vergis come to mind

I am slowly learning whom to attack and whom to avoid.

Good for you! That's FAR more important than champs or gear.