it seems to me, that you don't understand the main idea of this build.
I go with the defense tree, because I want to have a safe early game. Most times I can kill the enemies faster than they can kill me. You want to get fed by minions and champions in early game, and for this, you need to be able to survive. It's no use if you die in early game and feed instead of getting fed yourself.
And the masteries help the most. you have good life regeneration, which lets you lane longer, and you have reduced incoming damage (+ armor + magic resist), which increases the survivability of your shield, too.

the extra mana of the utility tree is useless, since you go back when you have 850 gold and then habe your catalyst. This item is even better than the MP5. We won't even need bluebuff during the whole game. Leave the bb for your friends, they can use it way better. remember, this game is based on teamplay.

ghost is better? in which case? you get slowed, or stunned, and ghost won't help you to run away. you can't even chase better, since you cant run through walls (with flash, you can) and flashing out of bushes and surprising the enemies with a stun followed by your shield explosion, is way better than running after enemies.

And yes, my comment "can't go mid or solo" is right. you are talking about different sions, like jungle sion, but this build is neither a jungle sion nor a solo sion, nor ad sion. You have to make yourself clear, that ap sion only has 2 abilities to deal damage. on level 10 you can deal around 600 damage. your enemy has magic resist so it is reduced to 400-500 dmg, so the enemy has to have less than 500 hp so you can get a kill. but guess what, when you have a laning mate, you stun him, activate your shield, and maybe attack once or twice and your mate is able to throw his abilities on him, too. This is much more dangerous for your enemy than you may think. you can focus better, and reduce life of the enemy much faster, letting him wonder what just happened when he suddenly died in an instant.

sry for my bad english, and thanks for downrating without even trying.

You have mostly tanking runes even though you are not building a tank. The defensive tree is unnecessary because it does not provide nearly the same defenses as utility does, let me explain. If you go into the utility tree you have the extra MP5, the extra CDR (not to mention the blue buff lasts SO much longer on him and CDR = faster stuns/shields which = more survivability, much more than what the defense tree will give), faster move speed to chase/escape easier, your summoner spells are refreshed much faster too. I will not comment on Flash because it has it's uses, but I still believe Ghost is better on Sion.

Your comment of "- can't go mid or solo" is completely false as well. He is one of the greater solos in the game. He is so versatile that he can take any role on the map whether it be solo, excellent duo lane or even jungle (blue buff required).