Damage scaling from enemies versus what you have available is insane; most enemies can mow through even larger formations fairly quickly, slowing progress to a crawl. exacerbating this is the exponential growth of alpha cost for pins beta onward with the tier ten pin costing 512 Alpha, tier eleven costing 1024, tier twelve costing 2048, etc.
Frankly, either enemy power creep needs a nerf, alpha generation needs a boost, or the fusing system needs reworking to be actually achievable in a reasonable time scale.