We report on a high-power picosecond all-fiber Tm-doped fiber amplifier (TDFA) seeded by a gain-switched laser diode (LD) in the 2 µm spectral range. A total average output power of 409 W (304 ps) has been generated at 320 MHz of repetition rate with 10 dB bandwidth of ~48 nm centered at 1970 nm. Over 140 W of spectrally flat supercontinuum (SC) output has been produced at 40 MHz of repetition rate with optimized fiber length. The 10 dB spectral bandwidth was 615 nm, ranging from 1965 to 2580 nm. The prospects for further power scaling of LD seeded ~2 µm picosecond all-fiber sources are discussed.