At the end of the game I had 39 unused stat points, and in principle could have easily switched to a ranger or mage.
I usually had a few spare skill points throughout the game, so one in Poison Arrow is not going to cause a problem. Actually, before getting the battle tower, I put 3 skill points into the encumbrance skill to be able to carry more loot, which was unnecessary (you don't need to keep common plants/rocks that are not required for healing potions, or enchantments you might use, etc), and those 'wasted' points were not an issue.
Before the battle tower you can easily switch classes. My warrior ended up with about 50 strength and 25 dexterity.
