Thanks for the honest feedback, you were right. I ran the numbers: since pheromone was also needed for Trails, using abilities felt like a waste, so people just held onto it. In my own test runs the Swarm almost never got cast at all.
New version is out: abilities are now free. Frenzy, Harvest and Swarm only have a cooldown, and pheromone is used just for Trails. Hovering an ability now shows how long it lasts and how long it takes to recharge. Harvest's numbers changed a bit (12s every 2 minutes) so the game doesn't lose its pacing.
Thanks for taking the time to write. Comments like yours shape the next updates, so keep them coming!