On PC, the game is a one-time purchase that typically includes all heroes and content by default. This is often the "cleanest" way to play with the full roster.
If you meant "Ashbite" (the baby dragon) instead of Andumpym, the strategy changes. Ashbite is a hit-and-run hero. In that case, replace the "Dump" step with constant kiting. However, for raw, AFK-style power, Alric + Necromancer spam remains unbeatable. On PC, the game is a one-time purchase
The phrase boils down to one truth: Bonehart is king, but Sha'tra counters bosses. Unlocking every hero gives you the toolbox; upgrading them correctly builds the house. upgrading them correctly builds the house.