I think some of the confusion comes from people mistaking "heavy duty staple" with a staple gun type staple or similar. A heavy duty staple is exactly like a common staple but maybe 1.5 times as thick.
I want to stress that it should be easy, but does not work 100% of the time because you do have to engage the barb just right. If you are too far in any direction it won't hit. The answer is NOT pushing harder, it is simply to try again. And this is the case with the staple OR with the proper "Mini-ISO terminal extraction tool". Last night after getting another staple complaint, I sat down at my kitchen table with a fully loaded connector (20 pins) and removed 100 pins with the staple and 100 pins with the "proper tool". It took me 121 attempts to remove the 100 pins with the staple and 119 attempts with the extraction tool.
The slight edge just isn't worth the expense. So I think those that are having troubles with the staple are, as suggested above, either using the wrong staple or inserting it improperly but would have the same trouble whether or not they had the proper tool.
I do appreciate the suggestion we supply the staples. One person even implied by email we shouldn't be "so cheap"

At one third of a penny each, I assure you it isn't because of cost. Not directly anyway. We originally were going to do this, but the time it takes to break off the staples and give each person 4 or 5... the medical bills alone would be preventative. It probably sounds like I'm joking, but our assembly workers drew serious blood that first day! So we stopped after the first few.
It won't help you early adopters, but we're working on designing a custom tool for the job that would be better than either the staple or the "proper" tool. It takes a lot of time to design, then submit for quotes etc and of course it may be impossible to do it cost effectively. But there have been enough complaints regarding the pin extraction that it is obvious we should do something to make it easier. I'm also working on better instructions that can make the procedure more clear, because obviously many of you are getting on just fine.
The procedure (staples) DOES work. But yes, it has to be better. Thank you for your continued feedback and patience and understanding.