I find that there's nothing wrong with multiple gain stages. Tube amps have multiple preamp sections too, if you bothered to look up the schematics. Having an overdrive pedal going into a distortion pedal roughly mimics the schematic and the sound of a marshall tube preamp, as marshall amps use 2 diodes for hard clipping after the preamp gain stages for the crunch channel, ala distortion, and inside the preamp gain stages, you have 12AX7s being pushed into slight saturation, ala overdrive. In short, having an overdrive pedal going into a distortion pedal mimics the signal going thru overdriven tubes into clipping diodes.