We have heat pumps with performance well over 12.5 EER (12,500+ btus delivered per 1 kw used). (the EER for resistive heat is 3.4)
It is possible to see the sort of savings that the author of that article claims. It's not typical, but it is possible.
For example, I installed three 1-ton minisplits in a house last summer (Fujitsu 12RLQ with an EER of 12.8). (so, 376% the power efficiency of resistive heat)
(granted, the installed cost on that system would be more than $4k, but that was a few years ago, according to the article, and he may not be including the installation cost)
One was installed in the master bedroom, one in the guest bedroom, and one in the living room. During the night, the owner would crank down the two unused rooms, and turn up the master bedroom unit. In the morning, he would come down and turn on the oil furnace for a few minutes to re-heat the house, then let the heatpumps carry it through the day. THe coldest couple weeks, he ran on oil alone. As a result, he spent $500 extra on electricity and went from 900+ gallons of oil, down to less than 200 gallons of oil used. 700+ gallons of oil saved, which costs a lot more than $500 these days.
These units were actually sized for cooling (the heat pump feature was just an added bonus of the high-efficiency models), so the results would have been better if we had planned the system for heating and cooling.
Under the right circumstances (only using one unit at a time on full, and keeping the others very low) and with top-of-the-line equipment, it's definitely possible to run heat pumps and save more than with pellets. You can also get special electric rates from the power company (at least, here in NH, you can) for a second meter which is used for an electric heat and/or hot water system, which would further reduce the operating costs.
In some cases, it can certainly work out. In others, it's not really practical. There's no "one right answer" for all situations, and it's important to consider all the options before making any decision of this sort.
Joe