I found myself with only about 45 minutes to play last night; so I tried the OMA Toob build for shits and giggles. You're right - it is very streaky, but I went just about 2:1 on each match that I played with it. I was playing Ground War, which is perfect for this sort of build since there are tons of people in the map. I got my Emergency Air Drop at least once every game!
The only problem is that when you decide to stop cheesing, your play style is all messed up. You get so used to poking your head around corners that you just shouldn't...
I'm trying to decide exactly what I think about this build. In reality, it's no more unbalanced than the ScavengerTube build, except that in some ways it's easier to build streaks with it (since you don't have to go hunting for more ammo). And if you just camp one spot, you're gonna get taken out quickly if the enemy is smart enough to watch killcams. I dunno...I need more time playing around with it to see if it's really worth it.
EDIT: Alternately, if the enemy is getting killed by toobs a lot, they could always put up a class with the blast shield. Problem is that almost nobody ever uses it.