Gate Drive Resistor size and/or Gate Driver IC
R1 is going to be more reliable in setting the LED current.  Q1 will start stealing volts from the base of the FET when Vbe (=Vr1) is 0.65V.  As such, the above will attempt to adjust the LED current to 650mA.  R2 is serving to limit this, but the semiconductor parameters keep R2 from easily controlling the current...across devices and conditions, the current limited by R2 will change dramatically.

I'd say stick with R2=100 and R1=0.65V/Iled (where Iled is the current you want to push through the LEDs).