So far the only evidence of this gap is pylon times for IOd to the gills builds.
That is why i changed my mind, no one has demonstrated this gap in other instances.
TW has three issues that I see as a set.
First it burns tons of Endurance. More than other end hog sets.
Second, it needs a lot of recharge. You spend a lot of time waiting for attacks. And even so it still feels like you don't have enough end.
Third, it doesn't have any quick fast attack outside momentum. So those enemies with just a sliver of health become annoying. Feels clunky to que up one of TWs ST attacks out of momentum to finish them off.
The first two seem like where the "TW isn't good till IOs" come in. With enough recovery, end red, and recharge performance must go up a lot. Seems reasonable, since the tradeoff for its drawbacks is big orange numbers and a bursty DPA increase.
So it really does seem that you are asking to balance a set around IO level performance.
Which they don't do anywhere else. Even the classic EM nerf was before IOs.