The argument that the paladin tank is too weak in comparision with the other three tanking specs is something often voiced on the official cesspool. When you check the posters you'll notice how they compare themselves with other tanks in similar gear.
They compare themselves with other tanks in similar gear gemmed and enchanted to do the job. And they compare themselves with tanks in gear that was designed for tanking.
There's nothing casual about going to work in a third PvP gear, gear unenchanted and half of it ungemmed.
Let's have a look at the difference between similar gear and a half-arsed lie, slot by slot:
Helmet enchant is 90 stamina and 35 dodge rating
Shoulders 75 stamina and 25 dodge rating
Cloak 250 armour
Chest 75 stamina
Wrists 50 dodge rating
Weapon, anything ranging from some selfhealing to proccing avoidance (so preferably Windwalk)
Shield 50 mastery rating
Feet 50 mastery rating
Legs 145 stamina and 55 agility
Belt a belt socket (which normally translates into 40 mastery rating)
Hands 65 mastery rating
There are also 13 gemslots of varying colours, one of which is a meta gem slot. Let's say you're skipping on six of these, two of each kind. That's 2 40 master gems, 2 20 mastery 20 parry gems and 2 20 mastery and 30 stamina gems.
Let's sum it all up.
110 dodge rating
40 parry rating
365 mastery rating
One perfectly useful weapon enchant.
Next let's place the result of two tanks with distinctly different quality of gear side by side.
One would be myself in an average 358 item-level and the other a paladin tank with 350 average item-level who I found on-line. I have padded out the 350 tank with the missing enchants (why did this not surprise me).
7353 vs 7318 stamina
1387 vs 1716 dodge rating
12.43 vs 12.80 percent dodge (this shows why agility is a surprisingly strong tanking stat)
1647 vs 1661 parry rating
13.49 vs 13.55 percent parry
3048 vs 1824 mastery rating
61.25 vs 46.4 percent block
The strategic difference between us is mainly one trinket. I'm running double mastery trinkets, and the other tank is carrying a stamina one. There is a smaller difference in gemming philosophy. I'm getting mastery but the other tank is scrambling to pick up as much dodge rating as is humanly possible.
We're pretty even apart from the not so minor detail of 15% block chance in my favour and 0.50% avoidance chance in his. In a raid he'd take close to 25% straight hits, and I would take 8%. Healers will tell the difference. To close some of that gap he has to drop 427 stamina to gain 4% block. Now he'd be way below the safety health limit for a raid, and he'd still be 11% block behind me. This is perfectly normal. I am, after all, geared eight ilevels better than he is. A rather distinct difference is to be expected.
Now, if I was to remove my enchants, what happens? I'd lose all of the the stamina advantage he has made from that one trinket. I'm dropping 0.50% in avoidance. I'm losing 4.5% block. And, of course, I'll lose my weapon enchant.
Incidentally it would be easy for me to regain that stamina. I slap on a trinket of my own and end up with almost exactly the same amount of stamina as he has. That would, however, cost me another 4% block.
I'm now matching his stamina, lagging 1% avoidance behind him, and my block is a mere 6.5% ahead of his. If I for some reason wanted to, I could convert some of that block to make up for that 1% avoidance. So dropping about 2.7% block would gain me that 1% avoidance.
I'm now ahead by 3.8% block but missing a weapon enchant. As I've chosen to gear in two agility based pieces we're also pretty much even on strength. The missing weapon enchant is Windwalk. The proccing 600 dodge rating has an uptime of close to 30%, so say 160 dodge rating over time. That matches about 2% block, so I'm still ahead by 1.8% block.
So, I might have failed to prove that missing enchants and missing half of the gems available fully makes up for an average of eight item-levels. It is damn close though. Cheat on another three yellow gem-slots and me and that tank are virtually identical.
If we start to throw PvP gear into the equation it isn't even funny.
We're not too weak -- they're too damn lazy to make up for two thirds of a tier-level's worth of difference in gear, and that's not anywhere close to comparable gear.