weeeeell...
If your AoEs are off then go solo smacks. cycle thru the group hitting them with aggro inducers (such as Heroic Strike or Claw) and even normal attacks work. so your current plan is smart actually yup.

"Tab-targeting" can be useful - you do your single-target abilities, but you try to use them on a different mob each time. Personally, I use Tidy Plates: Threat, with myself as a tank (making mobs I have aggro on have small, green nameplates, and ones I don't have large red ones). Mobs that are starting to pull off will have yellow nameplates, so you can target them and use a single target ability to get more threat. I'm not always fast enough, so sometimes I have to actually taunt, but it's pretty good. It's more precise, generally reactive rather than proactive, and less key-smacking than tab targeting, but tab targeting can be silly and target a mob in the next pack (annoying), or continually miss targeting some particular mob (resulting in you losing aggro anyway).

You also need to make sure your dps is focused on your primary target. Live by the mantra, "You pulled it. You tank it."

Well, as a warrior you shouldn't have mortal strike if you're specced into protection. And heroic strike and cleave share a cooldown so don't use heroic strike as a filler. Depending on your level, an improved revenge can hit two targets. Other than those criticisms your strategy is fine.

TIDY PLATES: THREAT PLATES! Highly customizable but even out of the box it will show a small green nameplate for the mobs you have adequate threat on and large red nameplates for mobs agg'ing on someone else. It is the single addon I couldn't live without as a tank and should be built into the Blizz UI.
Also works the opposite way for your DPS/healing roles so a great addon even for non-tanks.

As for your AoE issue: if you're not taking huge amounts of damage then you, as a tank, aren't required to focus on the mob you set as skull. If you glance at Omen and you have triple the threat on the mob than the nearest dps, go ahead and forget skull and start building up more threat on the other mobs. Don't wait until skull is down and people are burning down X before you start building threat.

@saeadame

I are a tab targeting fool. I do it so fundamentally I do it when I level/farm. I am pretty much Anti-Add ons and I know that's bad but Tidy Plates sounds very cool and helpful. I will make it my next venture for sure. Although I do use the standard UI aggro tool and it seems to work fine for me. Now if we can just have the poor DPSers who have been waiting 20-30 min for their queue to chill out a little bit and let us do our job

I have a macro for that:

/script SetRaidTarget("target",8);

that puts a Skull on my target so the dps know on which mob to focus.

As to marking, I've set 0 through 7 on my number pad to the raid marks. Hit the big old '0' and I get a skull, '3' for moon, and so forth. No fancy macros, just reassigned buttons, and you quickly learn to tap out exactly the mark you want.

@Daynthebold
I have to strongly disagree with "You pulled it, you tank it" in a pug 5 man. The only safe thing to do is to try your best to hold all the mobs.

I understand the point but unfortunately the same jerks who pull aggro as a dpser too often use a threat wipe after the mob hits them, dropping it off on a convenient healer or innocent ranged dpser. This happened to me several times while I was tanking a pug heroic last night and just about drove me crazy.

Heck, even if they don't wipe their aggro either the healer stresses and keeps them up or they die. If they live through it they are encouraged to do it again. If they die the mob is almost certain to go running to the healer.

If someone is doing a bad job by pulling aggro, call them out on it. If they apologize try to help them. If they ignore you or get rude kick them or drop group.

But if you're the tank, hold aggro until you die. That's the job.