That's why I added the 'retains Dex mod', changes one balancing factor for another. And makes sense, since the reason that a character didn't keep their Dex mod to Defense was that they had no way of seeing the attack coming.
Besides, by the time that a character can have Object Attack, they are either 9th level and only have one base class, have a level in five different base classes (to nip a talent each level since PsiTalents can be picked with any class), or something along those lines.
And by that point, the enemy's defense with their Dex mod intact is going to vary anywhere from 12 (unarmored Strong with a Dex mod of +0) to 20 and over (a Fast with some decent medium armor and a good Dex, or anybody with forced entry unit -armor), and since they haven't picked Telekinetic Combat Mastery (and have a BAB of +1 in the case of the five classes pal) with the average Defense probably around 15 or 16, they'll start to have a hard time hitting anything.
And Firearms are way better at dishing out the damage anyway: a Strong 3/Soldier 2 can easily get their hands on a Remington 700 hunting rifle by these levels, dealing 2d10+2 points of damage with a far better range and attack bonus than a psychic with Object Attack (probably d6+d8 within a range of 40ft at most).