Judging from your pictures, it looks like each of those jobs is about 6-8" around. If you filled 4 sheets of plywood with those and cut them out, that would certainly be enough to dull a bit, especially if the feeds and speeds were not ideal for the bit (which is likely given the nature of the Maslow as @ScrumdyBum mentioned earlier).
@MeticulousMaynard’s suggestion of a single flute bit should result in longer bit life (since it would b closer to ideal feeds and speeds), and aside from a high up front cost, would likely be cheaper in the long run if you bought something like this: