Turrets got a 3-to-1 compression some time ago in order to fix the problem that you always need to place them in fives to get anything done but at the same time AI waves got so much bigger that you still needed dozens of the new turrets to do anything.
It's nice that they're better than fleet ships but the lack of mobility means that a fleetship gets to use way more of its cap DPS in an engagement while most of the turret's cap is on another planet.
I do recognize that buffing turrets for sparse setups makes them overpowered in concentrated (e.g. single choke point) setups but since I usually go sparse I'd of course like to see a buff anyway.
I get the impression turrets are kind of meant to suck for multiple chokepoints. If you have a dispersed defence, you should be defending primarily with your mobile fleet, military command stations, and mini-forts.
I can only think of one way to make turrets better for multi-choke without making them overpowered for single-choke, and that's to give mini-forts a potent attack boosting power that affects a fairly large but limited number of turrets. Since you can only have two mini-forts per planet, if you only have one choke, you'll be able to boost half as many turrets as you would if you had two chokepoints (and hence four mini-forts supporting turret farms).
The problem with that plan is that turrets are limited to +100% attack boosting and military command stations already give turrets a substantial attack boost.