We present an experimental study of the performance of one-dimensional Distributed Read-Out Imaging Devices (DROIDs), based on two Ta/Al-based STJs placed on either side of a Ta absorber strip. We focus our discussion on the prospects of building large-format photon-counting imaging spectrometers for applications at soft X-ray energies. Tunnel-limited spectroscopical resolutions have already been demonstrated for optical photons. With a 20 x 100 micrometers 2 absorber we have measured an intrinsic energy resolution of 2.1 eV FWHM for 500 eV photons. This demonstrates that at soft X-ray energies resolutions close to the tunnel limit are also feasible for these type of detectors. A detailed analysis of pulse-shapes with analytical models allows us to assess the main parameters that determine the performance of these detectors. In particular, we discuss the dependence of the quasiparticle diffusion constant on the temperature of the absorber. Extrapolation of these models indicates that it is possible to extend the length of the absorber to 1.5 mm, without a serious degradation of the detector's performance.