Steroids

300 CP and up

Complain on the forums, strong people will be nerfed making it appear as though you are stronger. Similar to EP. For instance EP is always the bronze medal winner but it's a relative statement as it is only a three faction competition. If there were four alliances then they would not get a medal just for participating. That new alliance might be be third or second or first.

Just grind to have more CP points. Those can change a lot. And from what I can tell you I had the same problem. I completed all main story, cadwel's sliver and gold. My build there was a little bit too "tank-ish" (1 h & Shield and resto staff). It was very efficient because "high - level" zones back then were mostly empty. Most of the time I was able to solo dolmens and world bosses, etc.

But this changed now. Even if you are superior at tanking you will not be able to defeat world bosses solo. That's why I recommend to go DMG. There is no point in being tank in PvE anymore (unless you are planing some group dungeons).
Just get weapon / spell critical above 50% and a little bit dmg (60 attribute pints at magicka or stamina, whatever build you prefer). And upgrade weapon to at lest purple quality.

A few comments - while the zones that were lower level than you certainly got harder with 1T, the higher level zones also got easier. While I was skeptical (and my main was probably in the 400's CPs when 1T hit) that I would like 1T, it turns out I really have. I like that I can now go anywhere and have it be worthwhile. Yeah, I used to be able to go to the low level zones and just streak through every mob and have them melt - how much fun was that really? No XP, no worthwhile drops, mats only good for alts or others (which I did appreciate to a degree). Now the whole world can be used as a meaningful experience for all characters (unless you don't like that kind of stuff - endgame only type of player). On alts that are still leveling, there is never a need to either go or not go somewhere else due to forced progression - that is, the content either being way too easy (no XP or worthwhile drops) or way to hard (just die all the time). So overall, it seems pretty good.

Regarding character progression - it is still significant. I play low level alts as well as my CP capped main, and there is a huge difference in how they perform. Low level character scaling tends to balance out the stats - you may actually have more health and your off-stat than a CP capped character, but your main stat and things like spell/weapon power and crit are typically lower. You also won't have as many "high level" skills available, so generally won't be as effective. As you level up and get more skill points to spend, and level more skill lines, you will also fine tune your character to choose the best skills available for your playstyle. CP also helps out quite a bit - 15% to 25% bonuses in various areas can really add up to a significant overall increase in character effectiveness. My main 1 or 2 shots stuff that are actual fights on my alts. So even after 1T, I can certainly see that characters get stronger. It is more subtle than it was pre 1T, but it is certainly still there.

Edit: Just to clarify one thing - the world doesn't scale down to you, your character is scaled up to the world. The world is "CP160", and characters below that (or possibly CP150?) have a scaling algorithm applied to the character to bring it "up" to the world.