Hi Perry,
For the LDO, the best case efficiency for Vout = 1.2V and Vin = 1.8V is about 66%. So, the 42% isn't too far off from expectation with the FET loses taken into account.
For the VDCDC3, 58% is a bit lower but, we should remember that you are comparing the Vout of 1.0V to 1.5V. For buck converters, as difference between Vout and Vin gets greater the expected efficiency lowers. This could explain the difference that you are seeing. Otherwise, how about you short MODE to GND and re-take the data. You can send me a scope shot of the SW node and MODE pin too so, I can verify the IC operation.
Also switching loses dominate at low currents so, the DCR of the inductor should not affect the efficiency too much and you should mind the core losses.