Sacrifice 2 heads slot for 2 ECCM is a hard choise, you sacrifice range, dammage, lock time/range and even at 28%, if you have been sensor supressor, you have good change to be ECM again during your lock time.

btw I think this item shoud have a dedicated skill to improve it (like increanse ECCM boot signal by 3%)
with a such skill at 10, T1 ECCM will give +65, and T4 give +97.5. With such number, dual ECCM will be abused and need to be unique item