Play testing my Game with classmates: Two things i learned. Balance and how to make the game go by faster

I had two play tests with my dice game.
In both cases the players stated that the defender has a disadvantage, they say that while the defender has a 12 sided die that can cancel out the attackers roll, but they would still roll, mostly, a value under that of the attackers dice.
The players suggested that the defender get a die that has a higher value, such as a 15 sided die.

Also, players suggested that i lower the amount each player starts with, because if they start at 50, the game can go on for 3+ minutes. That doesn't seem like that long, but the players started getting bored somewhere between 1 and 2 minutes. It was described to me as " imagine if Rock Paper Scissors lasted 5 minutes, it would be boring."