It doesn't need to be overpowered to be boring, and it still makes minions of limited usefulness.
I started noticing this the most in my level 12 campaign, so I'll look at what a warlock and wizard of that level could do:
Warlock:
At-Will = Two-fold curse plus rod of reaving to kill 2 as a minor, pact blade to kill any that attack you (can use both, only need a +1 pact blade in the off hand), Slashing Wake Paragon ability to damage all those around where you teleport
Encounter = Doomsayer's Action (use an AP to damage all cursed, best used after triggering Rod of Corruption)
Daily = Armor of Agathys (Daily 1), Avernian Eruption and Hunger of Hadar (Daily 5),
Wizard:
At-Will = Cloud of Daggers
Encounter = Winter's Wrath (Encounter 7), Frostburn (Encounter 13), Burning Blood (Blood Mage uses Second Wind to damage every enemy within 10 squares), Storm Cage (Spellstorm Mage Encounter 11)
Daily = Flaming Sphere (Daily 1), Stinking Cloud (Daily 5), Wall of Fire (Daily 9), Wall of Ice (Daily 15), (technically also Acid Arrow 1, but whatever)
I believe that you can add more items to that list, but that's a pretty solid initial list.