So. I'm mostly interested in solutions, not just complaining. How do we get around this? Let's take about threat from the top.
Hit and Expertise are the two threat stats we're concerned with.
Hit is fairly obvious, it lets you hit things more accurately. The way it works out, you can refer to the following table to see how much hit you need at any given moment. Keep in mind, there is no mob in the game more than 3 levels above yours when you're at cap, so right now, raid bosses are level 88. As an aside, this means for your PvP set, you only need 5% hit.
|Difference in Level||Hit needed|
Expertise pushes your target's Dodge and Parry off the combat table. Melee DPS only need to push Dodge off the table as mobs can't parry attacks from behind, but tanks will need to worry about Parry. Expertise used to be really good for mitigation, as some bosses would gain a haste-buff any time they parried an attack, which gave tanks an incentive to stack Expertise, but that mechanic was taken out of the game and is no longer a factor. Expertise is purely for threat now.
The amount of expertise you need is the same for any mobs of a level higher than yours, but basically, 26 Expertise is the magical number you're looking for to kick Dodge off the table. Chasing the Parry cap is a loosing game and not worth the effort.
Okay, so why did you put that Hit chart up there?
Because you need to consider your environment, and what kind of threat output you need for that environment. The only mobs that need 8% hit are raid bosses. No other mobs in the game need 8% hit. Even heroic dungeon bosses are only level 87.
Why is this important? Get to the point, man!
Sorry, I tend to ramble. Unless you're tanking a farm raid-night to get through all of Tier 11 in 2.5 hours, you (generally) never need to worry about threat on a raid boss. Even if you don't have a hunter or rogue to give you Misdirects or Tricks, you should be able to have the raid sit on their hands for 5 to 10 seconds and with Wings, Inquisition and a small bit of luck, build up a solid lead before DPS goes nuts.
However, when you're clearing trash, when you're in a heroic dungeon, once you get some raid gear, build that threat set and use it.
So let's get set up for tanking dungeons and trash like threat kings.
A Hit cap of 6% means you need 720.65 hit rating. That isn't too much and honestly with items like Soul Blade, Elementium Earthguard
Paladins have it easy with Expertise. Glyph of Seal of Truth gives us an amazing 10 Expertise rating right off the bat. That's almost half the expertise you need total, from one glyph. You should always have this on. The rest you can get with some items here and there, or if you're feeling gutsy, with a Heart of Rage
One more thing - Glyphs and Talents.
If you're mostly only doing dungeons, you probably don't need Glyph of Word of Glory. You can safely swap it out for Glyph of Hammer of the Righteous. This one glyph will boost your DPS output to amazing levels on AoE mobs.
And again, if you're mostly doing dungeons and don't expect to raid tank, make your talent spec something like this (0/31/10).