I dont think this is viable at all, whats his ap ratio?

Why not Rylai's instead of Rod of Ages? It gives you an instant health bonus and 80 ap instead of the over time benefit of Rod of Ages, as well as a slow to your q skill, which you said yourself you will be spamming.

Catalyst = mana crystal
Sheen = mana crystal

= 800 gold wasted.

Rylai's also gives you an AoE 15% slow and a highly spammable 30% slow off your Q. How is wasting 800 gold on mana for RoA any better in ANY situation? You will contribute so much more thanks to the slow... as opposed to what... 150 extra health?

I did my typical analysis for a new character. I removed any value for Mp5 or Mana and looked at what AP items Shen would want, here's the ranked list:

Mejai's Soulstealer (20)
Guinsoo's Rageblade (8)
Mejai's Soulstealer (half)
Doran's ring
Rod of Ages (full)
Zhonya's Ring (100)
Abyssal Scepter
Zhonya's Ring (80)
Guinsoo's Rageblade
Blasting Wand
Amplifying Tome
Rylai's Scepter
Archangel's Staff (4k)
The Black Cleaver
Zhonya's Ring
Kage's Lucky Pick
Trinity Force
Rod of Ages (half)
Nashor's Tooth
Rod of Ages

Rylai's does help chase, I've tested it. Rageblade seems like a good choice since you'll be proc'ing and casting on 8 stacks often. If you're good and can protect the stacks, mejai's could be sick otherwise z-ring rounds out the AP items you'd want.

That third item doesn't seem very practical. I'd probably go with something else tanky instead. With some mpen, your overall DPS as well as burst damage would increase with a build like this. So, I'm thinking my tank items would be Soulfire cape(s).

edit: BTW, everything after blasting wand is a negative value item.