It depends on your tanking goals.

For Heroics where you don't need uncrushability:
490 defense (485 actually, but it's a technical thing).

When one is starting out with gearing, Stamina is more important to reach 10k health unbuffed.
But prior to the extra +6% stam talent change, most tankadins put +12 stam gems to reach that 10k.
Nowadays, 10k unbuffed is doable prior to getting raid drops/heroic drops.

Once the 490 def, 10k is reached. Getting the 102.x % avoidance is doable even prior to KZ gear.

For KZ tanking, with the Prince as a goal--lots of avoidance is better since it's a long fight with Phase 2 being more of a threat.
But for phase 1 Prince, lots of spell damage is nice to get some lead threat and have dps start early.
So, it's nice to have 2 tanking weapons: 1 with +spell damage (continuum blade, S2 gavel) for threat, and one for pure avoidance (mongoose, and a warrior-like tanking weapon Sun Eater).

Some like stacking +block "value" for multi-mob trash clearing.
Some prefer dodge > block > parry items.

For most tanking gear upgrades, that +Stam and Armor goes up, the Block, Dodge, and Parry of the itemization just varies for the same item levels.

But yea, Strength stat is currently the lowest of tankadin priority since 25 Strengh = 1 Block Value. Strenth suits a warrior tank more since it adds to block value, block value adds to threat, and strength translate to all damage.

A paladin's threat from physical weapon damage is small compared to +spell damage threat (SoR, JoR, Holy Shield, Consecration, etc).

If paladins scale with str/ap in Wotlk, what's going to happen to the +spell damage tanking set?