Its interesting that with mosfets you are dealing pretty much with rds on which is a resistance. Hence power increases at the rate of current squared. Adding more mosfets reduces both total power dissipation, and the dissipation per device.
IGBTs on the other hand produce more of a constant voltage drop. Its not linear, but the trend is that power tends to increase more linearly with increasing current. And adding more devices splits the current but does much less to reduce the overall voltage drop and total power dissipation.
Switching loss is a whole different issue.
At lower voltages mosfets will have far lower conduction losses, and adding more in parallel works especially well at reducing heatsink requirements.
IGBTs are pretty dismal at low voltages, and adding more in parallel hardly helps.
The situation reverses at high voltage. High voltage mosfets have higher rds on and much higher conduction loss. And power dissipation increases at the rate of current squared. You gain by adding devices in parallel but its a struggle.
IGBTs shine at high voltage, power goes up almost at the same rate as current.
This makes really high power a lot easier to achieve, especially with devices in parallel.
Moral of the story, work out your conduction and switching losses as you have done, and repeat with two or more devices in parallel.
Using two devices on a small heat sink may be a better solution than using one device on a smaller heat sink.
Then compare mosfets to IGBTs. There can be dramatic differences between all the various possible combinations, especially when you start looking at using multiple devices, and its all well worth the trouble.