Hey - I started compiling some of the dmg stats of minions and I'll post something here when I get a chance, but I think based on what you are trying to do with your build that you should make exactly 1 change very early to maximize the damage you can do. Do everything as you have been, but for your level 1 skill, choose shamblers. Immediately summon both of them, then get your siege and play like you normally do. You'll have to wait until level 2 for ground spike, so just take your time and farm for a wave or 2 if needed. You actually should keep playing like you do and don't re-summon the shamblers if they die (unless you are at the crystal), but as the goal of your build is massive damage/kiting, you will want the shamblers there (even if they die a bit early). I think once you see the numbers you will agree... but it does bump your dmg per second up a bit and you will have a bit more early killing/staying power in a lane.
I know you don't feel like you need shamblers, but once you see the numbers, I think you'll agree that you want them earlier. I did a few test games and the chance for a kill jumps up quite a bit before you get spike waves and increases throughout.
Or just quickly consider that you have an ability that can drop armor into the negative - the more minions you have hitting when that happens, the more dmg you can do. Shamblers are kinda crap, but if you just count on them for a few extra hits here and there early, I think you'll find them quite useful - as long as you can resist re-summoning them early as they aren't anywhere near as valuable as a ground spike or getting your other minions back.
And if you don't know or don't play like this - you should consider doing so - switch forms when you either don't have enough mana for spike or aren't using abilities/attacking. In closed form you regen mana faster and have additional armor. So, like a good tb, switching forms in between action is a smart move. Try it if you have not been.
edit - I still see a pretty big weakness to this build that I think folks could counter if they thought about it much. A reg, even not one that was in the same lane with you, could probably back you down effectively. Speed fire tb could probably do the same. Erb, like you mentioned earlier, could cause you some trouble. A hybrid or minion oak could like do the same. Anyway, I think the full dmg spec QoT can certainly serve a good purpose for early lane control and potential late game pain against quite a few dgs, so its certainly good stuff. I'm just wondering if there is any good counter with a build like this and a reg snipe spamming, etc. Early snipe spam would force you to back down without much regen, etc... which would kill your leveling... which would kill the build a bit. Anyway, that's the type of stuff I think about when builds get discussed. How would I beat it. And I'm thinking I'd just go speed fire tb or reg (reg would be easier).
Still - fun stuff. Hope you keep working on the build and come up with something quite badass.
If you do come up with a game where you feel like it was good against pretty decent opponents and your build worked well, please post a replay. I'm sure a few of us would check it out.