The tier system here is somewhat different from what you normally see in Phasecast's videos:
A: must-have troops that form the core of most strong formations.
B: nice-to-have troops that complement A-tier troops
C: fill-in troops that fill the roles of some A/B-tier troops
D: troops that most players avoid using
Troops that form the backbone of most strong army formation.
Because they are fast and can revive once, Undead Soldiers are perhaps the best front-line melee troops. Some players use them for back-line defense as well.
They are one of the best counter against Peltasts.
Peltasts can kite melee troops (they run backward while attacking melee troops). They have short ranges when compared to archers and catapults.
Frost archers are perhaps the most overpowered troops. They can freeze enemy troops and hero after five attacks.
They cannot be targeted when moving and can deal great damage to enemy troops due to their AoE attacks.
Troops that can be used to complement A-tier troops
Although they are slow, they can deal heavy damage to enemy's range troops. Catapults work best when there are two or more of them in the battle field.
Ice mage's ice detonation skill can slow down enemy troops. Some players use ice mages in place of catapult, and some players use a mixture of both.
Bandits throw knives five times at the beginning of a battle before charging into enemy. They are good filler troops.
Harbinger of fire can attack multiple enemy units at the same time.
Of all troops, paladin has the most combined health points. They can be used as either tanks or support troops.
Brawlers raises a shield after 4 attacks. They are often used in formation that prioritize blitz attacks.
Ghost assassins blink to the back of enemy troops at the start of the battle. They are often used to trigger goblikazes in the enemy's back line.
Goblikazes create explosion that can burn enemy units for 3 seconds. They are often used at front and back lines.
Sacred swordsman, demon, and meteor golem are high HP troops that are capable of taking on multiple enemy units. They are especially useful in countering heroes like Zeus and Ivan because they can last a long time.
Troops that can be used as replacement for A-tier or B-tier troops.
Pilgrims can heal friendly troops. However, because of their low HP and defense power, they are often killed before getting their skill off.
Inquisitor is generally used as replacement for Undead Soldier.
Cactuses can reflect damage from enemy melee troops. They are generally used as replacement for Undead Soldier and Goblikazes.
Priest Mage can deal damage to a line of enemy units. In general, ice mages are more often used in the arena, though some players seem to prefer Priest Mages over Ice Mages.
Soul Hunter, Beast Master, and Witchcraft Totem are generally used as fill-in when high-HP tanks are needed. They are generally replaced when better legendary troops become available.
Troops that most players avoid using, largely because more useful troops are available.
Rhino Knight is a relatively new troops. There isn't yet any consensus as to how it should be used.