Even if you know that the load added by the devices in the loop totalizes more than 250 Ohm (that is the smallest load needed to communicate HART). It is NOT recommended to drop the classic 250 Ohm resistor from the current loop.
Consider this.
Let's say you are going to do maintenance on one device in the loop.  When you remove this device from the loop and take it to the workshop. Let assume that you shorted the 2 points where this device was installed, so the loop keeps closed.  In this situation, the total load now could get lower than 250 Ohm based on what was left on the loop.   If this happens, the HART communication in the line is compromise and may not work anymore.
On the other way, put in mind that too much load in the line may need a higher voltage power supply for the loop.