Spell Damage is important for threat. For Kara tanking, a Spell Damage weapon (minimum ~120 such as the Crystalforged Sword) with Superior Wizard Oil should suffice if your group doesn't vastly outgear you (in which case they'd have to hold back). For Gruul it would help if you could push that 80 or so higher, and the same Spell Damage should suffice for Mags.
Beyond a Spell Damage weapon, more Spell Damage is important, but takes a back seat to survivability. The only true Warrior tanking gear is gear that can ONLY be worn by Warrior (ie. Tier gear) -- tanking plate is made for both Warrior and Paladin tanks. Tier 4 is a perfect example of how many pieces of ARMOR that have Spell Damage on them are NOT good for tanking. The Tier 4 Shoulders are the only really good piece of Tier 4 gear for Paladin tanks. Of course, Tier 5 Shoulders are stupid easy to get (Loot Reaver ftw) and the ZA shoulders aren't THAT hard to acquire either. Both are superior to Tier 4.
Warrior threat stats such as Block Value, Hit Rating, and Expertise benefit you as well. Block Value is purely a mitigation stat for us, but Hit Rating and Expertise are both valuable threat stats as well as a way to ensure your Shields and Taunts always hit. Really good Spell Damage armor doesn't show up until Tier 6 imo, though there are a couple of decent Badge pieces. It's kind of like a healer stacking Haste. You only start to REALLY stack it (on lots of pieces) after you are able to maintain certain defensive stats and HP levels. For that to happen, you need a fairly decent item level because Spell Damage uses up TONS of budget compared to other stats.
By the time you're at a Tier 4 farming level (and ready to step either into Tier 5 if you have relatively little experience raiding or Tier 6 if you know what you're doing... the gear jump isn't really that bad, Tier 5 is more of a training ground than a gearing step) you'll probably have Spell Damage on your:
Weapon (likely ~200)
Chest (Badges)
Legs (Badges)
Boots (Badges)
And MAYBE on your Shoulder (Tier 4), Shield (SSO Rep), and Belt (Badges).
Tier 4 gloves are too crappy to justify the Spell Damage unless you want an AoE threat set. Same deal with the Tier 4 helm.. I'd rather use an Eternium Greathelm than that, and if you're an Engineer definitly not.
With just those pieces adding to your Spell Damage, you can generate enough threat to tank for progression in Hyjal. You'd probably need a little more to keep up with DPS that are able to farm Hyjal.
Some important items that people often mistakenly classify as "Warrior" gear:
~Badge gloves (Okay.. they aren't great, but they blow Tier 4 away)
~Badge helm (Same deal)
~ZA Boots (They're AWESOME and blow both of the Badge boots away in terms of survivability, but you might want to take the 2.3 Badge boots for their Spell Damage if you have enough and don't want to wait on these to drop)
~ZA Helm (Unless you're an Engineer, you aren't likely to beat the ZA helm until you get your Tier 6 off of Archimonde)
~Aldori Legacy Defender
~Bulwark of the Amani Empire
~Kaz'rogal's Hardened Heart
~Bulwark of Azzinoth
Okay... so if ALL FOUR of those shields are considered "Warrior" shield, what does a Paladin tank use? That is THE (Raid) Tank shield progression right there Pre-Sunwell and a Paladin needs them as much as a Warrior. The same goes for lots of other gear. Just because it has hit and block value does NOT make it a Warrior piece. Just because it doesn't have Spell Damage does NOT make it a Warrior piece. You're trying to survive, you stack gear that makes that possible.
In terms of intellect. No. You don't stack Intellect at all as a Paladin tank. Expect to have between 4200 and 5000 MP your entire tanking career. If you have more, you've sacrificed some important stat (likely a defensive one) somewhere to get it.