I've been going through the Titan Quest Skill Calculators, and I know of all the left click attacks that you use for a main attack. Warfare has Onslaught. Dream has Psionic Strike. Spirit as Ternion Attack. Rune has Rune Weapon. Rogue has Calculated Strike. And Hunting has Marksmanship. None of these attacks has a recharge time so they can be used indefinitely as long as you can meet the energy needs.
But the other masteries, Earth, Storm, Nature, and Defense have no skills that you can use as a left-click attack without recharge. So if you make a character using two of those masteries, you'll have nothing special. Which means you may need to just use the basic attack. And some of the other masteries listed above in the first paragraph have the same problem if you use an attack style or weapon that cannot use the attack. For example, the melee Spellbinder, the Spear Warden, the Guardian, melee Paladin, melee Juggernaut, etc.
So what do you do if your character has no left-click attack that lacks recharge?