Tyranitar is a great all-around counter (and also double-resists Psychic). However, you want to temper this with a bit of glassy DPS too. Consider a mix of Tyranitars and Gengar/Mewtwo with Shadow Ball.
Also consider that Focus Blast is the most devastating move for a Tyranitar. You absolutely should try to dodge it as it will 1 hit Tyranitar otherwise due to being a double-weaknesss. They by no means are a bad counter against this moveset, but you should be using a couple glass cannons in front and dodging Focus Blast.