Hi,
I've noticed the very short TWF attack range too, on my rapier-wielding ranger/rogue. It's at the most acute when chasing mobs, even if they are slower than or move at the same speed as you.
I don't remember the update or patch, but some time back I thought I remembered reading that the hitbox for unarmed combat was made larger to improve the playability of monks. If there is actually a difference between hitbox size for unarmed and armed TWF combat, perhaps the armed combatants could get the same improvement.
Lastly, it would be good to get some more information about why TWF is not going to receive a melee power buff. As others have mentioned in this thread, not all TWF builds are tempests. If it's because you're worried about making one subset of TWF builds too strong with a melee power buff, perhaps you could identify that subset, and start talking to the community about what can be done to assist the other TWF builds.
My own main's current build, a twf ranger/rogue who normally runs in shiradi, is about to fall through the cracks here, and miss out on most of the boosts associated with this rebalancing of the combat system (both ED and fighting style). Why this has to be the case, I still don't know, given that he isn't currently anywhere near the top of the DPS tree as things are.
Thanks.