Tax counters are surprisingly effective in edh 1 on 1. The curve is really high and people often don't play around 1 offs like daze/pierce etc. It's also very useful in counter wars because usually the opponent will leave exact mana up for a counter spell. The early game in 1 on 1 is very important because once you stick a zur and necro, you no longer care for dead draws.

Also generals get + 2 mana cost every time they die. You will see a lot of people paying exacties mana for their general later in the game.