This actually plays alot like yours
Yes, I've taken time to re-read that PM, in fact, because I thought the builds are similar
Seriously, I think your analysis is good and does make sense. Why do I advocate a counter-logical skill progression, then? Well... If DG online were full of skilled aggressive teams that are 100% aware of QoT's benefits and limitations -- I would be crushed by your logic. However, that is not the case. I have devised my build desperately trying to find the middle ground between "the safe QoT" and "the QoT that does the essential QoT job done". The essential QoT job, in my opinion, consists of: saving/helping with BS; dealing with later game creepwaves; destroying enemy mid/cit.
Early GS may sound wonderful in theory. Practically, though, in casual matches: (1) you are hideously unsafe and always need help, (2) you are always oom, since you have to purchase Unbreakables first, and (3) the teammates usually don't reap the benefits of those early GS debuffs, just leaving you to perish when you port in and do a glorious 250-500 AoE that tickles those squishy Regs and TBs.
In skilled matches, on the other hand, people are way too aware of what you can potentially do with those seemingly crappy AoEs. The chances are, you won't hit a single opponent with GS. I know I get hit with GS maybe once per 5-6 attempts when I play Sed vs QoT in lane: way too aware of the exact skill hitbox, and anyhow, hybrid QoTs signalize they are going to ground spike you several seconds before (it's not open->ground spike, it's more like ooooooooooooooopen->ggggggggground spike).