Instead of letting axe weight do the job, with Fiskars you need to do the job.
Way I use Fiskars is that I kind of pull down whole axe instead of pivoting it around end of handle, it seems to work better when left hand keeps pushing it down, that is because Fiskars lacks of weight, I believe.
Vince has made nice edge to that Home Depot axe, I have exact same axe head in a axe I bought cheap, I guess they make those heads in China and put to different handles, then sell as different brands.
I did weld over 4 pounds of steel to back of that head, old axe head and some other bits of steel, with good edge and added weight, that thing destroys everything I have had under it.
Fiskars is nice, but it is too light for harder stuff, they use fresh birch at demos of Fiskars and for that it is great tool, not so great for something challenging if goal is to split rounds to two halves with one strike.
If one takes small cuts at edge of round, Fiskars is quite nice, at least with Pine and Spruce that works quite nicely, but you guys have much more challenging wood to split, I'm quite sure that with good sharp edge and 10 pounds of weight my cheap axe will do better job than Fiskars on that challenging wood, but I have no way to test that out.