Tyrant usually sticks with the Hormagaunts. This allows for a little extra.. punch to the combat. Warriors stick with Termagants and they reduce enemies to dust while hiding in cover if available. Zoanthropes follow the trygon. this group being the "biggest threat" will be aimed at the most allowing for hormagaunts and tyrant to reach the lines when the trygon goes into assault.|
Hive guards snipe vehicles. Biovores keep them hiding. Gargoyles beeline through this cover into the enemy snipers or other annoying support. Genestealers poke thier dirty noses into outflank hopefully aiding the correct side. And the deathleaper. those flesh hooks eat at any commanding unit quite effectively and sometimes goes to fight the terminators.
Carnifex with the bio plasma eat units like termies up and also small tanks.