I assume you are wearing Scale because your Constitution is not good enough to get Plate.
As a Fighter your main job is to lock down enemies, as many as you can. This means being surrounded by monsters. At your level Shield of the Barrier Sentinels is an option, if you are flanked a lot it is quite good. Especially combined with Ubiquitous Shield. This does not increase your AC, but prevents it from being reduced, which is mostly the same thing.
With a good Charisma, Harlequin Style and Brash Strike you can increase every defense against one target.
Bloodiron Armor does something similar, but without any restriction on the power you use.
If you have all this, or as many as you can get, focus on other defenses, DPR and status effects. At your level being dominated, stunned or immobilized is more dangerous than mere HP loss. It does not matter how many hit points you have if you are dominated and slaughtering your own party.
In your entire carrier you get 18 feats, and Toughness is not in the top 30 for the most builds. For this reason I consider Toughness a trap, you should instead increase your defenses, accuracy or damage.
How defending works
Your job as a defender is to discourage enemies from attacking your teammates. Also you have to be able to take the resulting attention. You have to keep a careful balance between these two. Raising your AC (defenses) sky-high helps with the second, but hurts the first.
If an intelligent enemy has much better chances of hitting your controller than you, it will go for it. It will have a -2 from the mark, but your AC might be as much as 5 higher even so. If your hit chance is low, or your damage is meager, the monster has no real incentive not to attack the target that has fewer HP to begin with.
So a good defender Fighter build (there are quite viable striker builds) goes like this:
- Attack negation like Shield Push or Lashing Flail can prevent an enemy without reach to actually hit an ally
- Increasing hit chances as both of the feats above require a hit on Combat Challenge
- Increasing Combat Challenge penalty with Daunting Challenge as sometimes you can not move the attacker out of range
- Increasing defenses with Improved Defenses and any way to AC
- Increasing condition tolerance with Martial Resolve, Superior Will and similar feats
- Increasing damage, Frostcheese comes to mind
This is the order best used against a DM with good tactical thinking. I have played with some who always respect marks, against those you can forget about 1, 2 and 3.