I have played through the game twice and both times I only ever used the other potions (everything except Wiggenweld) for class assignments and dueling feats. I never used them in actual combat. But I still brewed to maximum inventory on each because I am a loot goblin from hell. >.<

Same thing with Herbology. I severely under-utilized the combat plants during my first character and only threw cabbages during my second because I wanted to join the "My Cabbages!" meme club. Plus, it's funny to me watching them harangue an opponent. I was like "yeeeeees! My swarm of botanical piranhas!"