Hi,
I´d say it does ot work.
Why:
* Each power supply has it´s own regulation loop. It tries to maintain stable output voltage by adjusting output current.
* but each has it´s own setpoint. Although all say 3.3V, each has it´s individual tolerance, individual drift per time, per temperature and drawn current.
* no one knows what happens when all three are hard connected in parallel. Usually one will deliver the very most current, while the others are lazy. And for sure the one that delivers the most current will first go into overcurrent shutdown ... causing a domino effect.
* no one knows whether they are stable and during power up (1) and during normal operation.
* adding with diodes, may improve stability, but then the ouput is more 2.8V than 3.3V.
* adding with resistors, may also improve stability, but the power up problem still exist, and the voltage drop problem. Also one can not guarantee the current distribution to 1.0A and 1.2A..
(1) Some details to "paralleled power up situation"
I had a DCDC controller (expensive and very good brand) that did not like when the output voltage was normal (3.3V in your case), while the input was shut down for a short time. If I remember rigt, then this had to do with soft start, which was active at low output voltages. Since here the output voltage is not guaranteed to be close to zero (because the other supplies) the soft start never was activated ... causing an explosion of the SMPS IC.
This IC was not suitable for big capacitors at the output, or goldcaps, batteries, paralleled supplies.
Klaus