By the way, a +3 shield as far as game mechanics are supposed to go, shouldn't stack with the shield spell (As they are both supposed to be shield armour).
As Pere said, you're biggest problem will be your AB. You have 11 AB with base weapons at level 20. 11 AB, +4 from GMW, +4 from greater heroism and +2 from bulls strength still only bring it to 21, which is sub par for a meleeist especially with only 2 attacks per round. My level 15 tank character gets to only slightly less ac then your 53, as he gets to 45 if I recall, and he gets 4 attacks per round at +28 unbuffed. So yes, you are hard to bring down by AC and great work on that, but you'll have a hard time dealing damage.
That and your saves are low enough to cause problems. I know Kor has always run into problems with spells, most enemies can't touch him (Including the ability to tank Canite Harbringers for a while), but one warlock can chip his life away fairly quickly, and he has more then double your saves. Sure, you could raise your saves between Nightshield, Conviction, Superior Resistance and Greater Heroism for a total of +15, but alot of enemies dispel.
Lastly, your life is very very low for a tank. I once tried making a strong tanking rogue. He is quite good, he has higher AC then most fighters do, and he hits hard (he feints to get sneak attacks, while being full shielded with tower shield and fullplate) ... But he doesn't have enough life to take more then a few hits. There are lots of ways to get past AC, be it by spells, or rolling a natural 20 but its not always that hard. False life and Greater Heroism only help so much.
What could be interesting for you to try, is a guy focused on Polymorphing. He could get level 7 spells, maybe 10 EK and 6 sorc, 4 palemaster perhaps. Then use Tensors Transformation with this heavy buffing so you don't need to worry about your low strength/dex/con because they are set to 20. You also get to keep your buffs. This could work for Cleric as well with War (Or fury, I forget) domain, which gets Tensors at level 6 spells, and then you get some other goodies like max BAB from Divine Power, and +6 strength. ((Opps went off on a tangent.))
But yeah, there are many builds that are good, though most of us don't classify 19sorc/1 cleric as a sorcerer because adding 1 cleric just doesn't really fit into our perspective. Not that there is anything wrong with it, but when we were talking about builds, as Pere said, its mainly builds that lean heavily into a class, or have roleplaying reasons for their dips.
You seem to be under the mistaken impression that us saying hard to level = not a good class. Nowhere in this discussion has anyone said that Sorcs and Wizards aren't powerful, you're right, they are (I know at least a few folks who curse the fact my completely sub-optimal sorcerer can effectively wipe the floor with their powerbuilds not even trying, did you miss the part where my main is a Sorcerer?), we simply said that they're hard to level, especially at low levels.
Yep, I know my main, a wizard named Hyel, has beaten a level 20 powerbuilt fighter easily, when hes only 17, (Though thats partially because thats his specialization). Hyel has also done fairly good in a battle against Phelan, when Phelan was 3 levels higher, and had alot stronger capability for melee combat. (Though he lost horribly in another contest

.
All characters will have their strengths, and their weaknesses and in our opinion the difficulty of leveling a sorcerer or wizard is its weakness. Not to say it doesn't pay off, they are just late bloomers.
Oh and as a side note, I think I've seen higher then 59 AC one time in Pandemonium when we boosted the AC of a guy with already very high AC. (One who normally doesn't have any spells recieved some wizard and cleric buffs giving him +7 AC).