Maximum resistive load on 3 phases 400V, 16 A
You are absolutely right that you can draw less current through each resistor when connecting phase to phase. The actual current for each resistive element will be 9.23 A not the 11 A you calculated.

The current flowing in each line is limited by the wiring for each phase, which is rated at 16 A continuous. No matter how you connect the load resistances, there can only be a 16 A line current in each phase wiring run.
You have two choices ...Delta or Wye connected loads. 



In the case of Delta connected circuit the line current (that flowing through the wiring) is 1.732 * the individual resistor current when at least two resistive loads are connected to that line. The converse being with a 16 A line current limit, you can only get 16/1.732 --> 9.23 A flowing in each resistor. This limits the total W to  3.693 kW per resistor and 11 kW total. 

In the case of Wye connected load resistors the line current is limited by the wiring to 16 A, the voltage across each resistor becomes 230 V --> 3680 W  so total power is 11 kW.  

Net result is that you can only dissipate the same total watts in either Delta or Wye connected loads.