If the PC with the Area attack is getting a dozen hits out of a dozen attack rolls, either he's using loaded dice, or the encounter was not built properly.
Well - yes. If taken that literally. But what if that one PC has a friend.
To take Zombies as an example (either Rotters from the MM or Pack Zombies from Treasure of Talon Pass; and it has been pointed out elsewhere that zombies make poor minions) - with their
best defense of 13/14, and a reflex defense of 9/10, you are typically going to take out 3/4th of them with any attack - so after two area attacks (usually versus reflex) you are going to have only 1 in 16 (<1 out of a dozen) surviving.
So lets consider Kobolds instead. Now we have a reflex of 13, so your first levels dragonborn and wizard are going to kill half of them per attack. Better, but the odds of any surviving to reach the PCs is still pretty slim. Barring an ambush, 3/4ths are dead before they reach the party. And when they do, those members of the party who won initiative will have delayed an attack until they get into range and will kill (statistically) half of the remaining before they get into range. Which means that 7/8ths of any group of minions will die before they can reach that party, with only the expenditure of a dragonborn breath (encounter, pretty much only good for minions) and a few at wills. And the one or two remaining from the original dozen get one attack before they die.
If they minions can't reach the party and attack first, they will never get an attack.
So yes, the alternative (aside from starting all encounters with a zerg rush, or making all minions ranged attackers) is to go in and manually edit all minions to get their initial survival rate up to where it ought to be. But is that
really any different than (for example) redefining the effect of a hit so that some survive and are bloodied? Either you follow the RAW and nearly all die to two area blasts or you don't and you manipulate the rules/numbers to get the survival rate you want.
That said - I do agree that that these are
not well built encounters. But I think that they are
typically built encounters. Any encounter that bunches minions together (as, for example, was done with every minion encounter in Treasure of Talon Pass) is bad encounter design. And this doesn't necessarily mean they have to be a mass at the start of combat - the simple need to close with the party (especially when combined with non-minions that hold back and don't attack during that first round) is usually sufficient to crowd them adequately unless you put each minion on its own initiative - in which case you've undone any potential decrease in bookkeeping you gained from the minion mechanic.
Only when the minions are scattered amongst non-minions so that you can only target one or two with an area attack are they useful. But that doesn't seem to really fit how most people see/use them.
Carl