Morello's and Nashor's would be CDR overkill. Actually, with 21/0/9 masteries like you suggest, anything more than Randuin's would be overkill at that point; you could just do Nashor's, masteries, and runes for 40%, for example. Morello's should probably be taken out of the build, because now it thinks you're selling Trinity, and Trinity is grayed out. :-/

You probably get rofltons of spell vamp when you ult... I can hardly imagine.

I kind of want to see a Tear of the Goddess in there somewhere, too. Hard to say which way to take it in a hybrid build, but it's 500 for your shield either way.

Blitz is by far my favorite character, and I usually play the AP Metatank that most people are used to playng, but I finally looked into a DPS build! Honestly, I'm not sure about sorc's shoes with this build, and I would much prefer going for movement speed 3 boots, with his W and ghost makes a nasty fast chaser Blitz. I also would move the Trinity Force before Banshee's Veil, but that's just my opinion! :)

Great read, good build, and the best character.
Way to go man,
PHouse

I used to go 9/0/21, but I perfer the more dps with the offensive route with the 21/0/9.
Overdrive first is a good idea too but, if you ever juke in the bush, the lower cool down on your power fist may help you at times, and also if you max power fist first, with the lower cd and a sheen, it'll proc faster, dealing more damage.
Nashors tooth! ;D
Catalyst first is good but I go hybrid so I don't find it necessary to make one, after a catalyst, I don't find it useful to make a RoA if your going a hybrid build, and banshees won't help too much for a hybrid build during the early games.
Try hextech on him! It's amazing. ^^ Thanks for feedback.

like it, I play similar build, but I never try Hextech Gunblade.

My suggestion:
For the mastery I go for 9/0/21 I find utility more usefull.
I max overdrive instead of power feast(1 point on it is all u need).
Nashor's Tooth is mandatory for CDR.
I like start with Catalyst the Protector for more survivability.

To be honest it is, but with blitzcrank, you'll always be ganking and farming. It's very easy to get assists/kills with him, and also, because of teleport + your movement speed, you should beable to one shot creeps with your ultimate. Because the ult is around a 27 second cool down, it'll be easy to farm with him.

Quite expensive item build isnt it?