@klog I've encountered similar issues using digital servos and Photons that isn't necessarily related to power draw issues, but more to noise on the servo's power lines, and how often you were polling the servo position updates. The 'ringing'/oscillation/feedback loop can destroy a Photon's voltage regulator, when the Photon struggles sharing power with the noisy digital servo, while at the same time trying to signal the servo via PWM. In my case, without filtering caps, the 186mA digital servo consistently murdered Photons when the servo arm moved to its extremities at high refresh rates. While the voltage regulators can be replaced, it's not something to do on a constant basis.
Here's the discussion below from that episode. tl;dr: besides catering for sufficient power supply, add filtering caps and check how often you're updating the servo position.