The biggest challenge was the damage calculation. Early versions used Scrabble-style letter values, but that made the game too predictable: the person with the most high-value letters always won. Meh...
The solution was to decouple word value from damage. Damage calculated by comparing the two words in the battle rather than absolute scores. A 12-point word against a 10-point word does 2 damage, regardless of how those points were achieved.
This meant a carefully timed 8-point word could be devastating if the opponent played a 6. It shifted the focus from hoarding high-value letters to reading the table and knowing when to strike.
The special cards went through a few iterations. Early versions had too many; the game became about the cards rather than the words. Too few and they felt irrelevant. Five felt right: each one distinct, each one memorable, each one creating a story when played.