Abilities are not great (they don't create new strategies or interesting synergies), but they're not completely useless:
- "Improved thrust" is in fact the most powerful combat ability. Comparing to the default thrust, it does 3 points of damage (vs 2) and costs 2 points of energy (vs 1). That sounds underwhelming, but in practice it means that you can kill a zombie in 2 turns (vs 3), a fay in 1! turn (vs 2) and a witch in 2 turns (vs 4). It's a big and important difference.
- "Swing" only makes sense when you're fighting more than 1 enemy. I think it's a decent starting action if you're using the default thrust (not the improved one). Also, it creates a quite powerful combo with the unstable shroom against 3+ enemies (because shrooms do more damage to already damaged monsters).
- "Slam" too only makes sense against multiple enemies. It does the same amount of damage as the default thrust and costs 1 more point of energy. In addition, it shuffles the enemies and interrupts their powerful moves. It's rather situational.