Wow, I didn't read the whole thread but a LOT of people on at least the first page completely missed the OP's point/argument. Yes, a level 30 player is stronger when facing off against a level 10 player (pvp), and the level 30 player is stronger against a level 20 mob then a level 10 player is against a level 20 mob.
BUT
A level 10 is much stronger than a level 30 when facing scaling content, so dungeons AND outdoors content that is being scaled to your level, which is all leveling content.
And the 10 isn't just slightly stronger, they are significantly stronger. Took a level 10 tank into a dungeon and I could solo 3-4 elites at once (with just basic BoA gear, nothing special or game breaking) in record breaking time/dps, only bosses are overly challenging. Go ahead, try that at 30 or 40 and let me know how it goes. Even if you could do it, it would take 2x or 3x as long.
So the OP's point is valid. The scaling is out of whack. As you level and gain more abilities/talents/stats you actually get weaker versus equal level mobs. It is just like people leveling in old BfA and losing power as they leveled up from 110-120, with the worst being levels 117-119.
My level 10-15's alt can defeat most normal mobs in 1 ability, 2 max. But by level 30 they're up to about 7-8 hits/abilities per normal mob kill.
Now, is all this a big deal? Not really since pvp has brackets and pve leveling is whatever. But you shouldn't feel yourself getting weaker as you level up. Sure, you might spike a little RIGHT when you get a new or improved ability/talent, but you're not going to be stronger than your level 10 self.
The power difference is enough that I wanted to make a level 10-12 "twink" tank to help boost friends through dungeons (you know, while doing 50+% of the group's overall damage), but if you turn off EXP you hurt anyone else grouped with you. Oh well..