I completely disagree that any of the specialists are not useful.
They all fit into a brilliantly constructed Rock Paper Scissors hierarchy.
None are so powerful that they can't be countered by another.
Each has utility at different points entirely dependent on the strategy you adopt at that moment in the game. I favor those with global abilities because they play into my general play style, but if I'm not dealt what I would otherwise choose, I have to adapt. If I cannot adapt, that isn't a failure of the games mechanics, it's a failure of my strategy.
If you don't get the "powerful" specialists you want, you may need to play more diplomatically, cutting deals, fly under the radar, appear to be more meek.
I love that this game doesn't boiled down to "tank rush" every time and that someone dealt "all the powerful" specialist can still be out maneuvered politically and come in last.
Achieving that balance is so delicate. I really applaud the skill at which the game has been balanced.