Rystil Arden said:
Let's say we've got a Great Wyrm Blue. The wizards can easily stand such that he's not going to take out very many in one breath weapon. If you assume large killings on the part of the dragon, that's fine too, though we may want to knock the wizards' number up to 50 in that case. 50 will kill the thing in two rounds without casualties and can easily do so in three rounds even losing 10 or 15 men per round.
EDIT: Based on your last edit, I think you've forgotten that I'm explaining why the force attack would be overpowered as a touch attack, not in its current incarnation as a non-touch.
Even as a touch attack, the Needle of Force is hardly overpowered, even in your overblown example. Let's take a Great Wyrm Blue Dragon, as you said. It casts as a 17th level sorcerer. It has 8th-level spells - four of them, to be exact. Let's give it three buffs - Persistent Scintillating Scales, Persistent Shield, and Extended Greater Mage Armor. This costs it a fourth-level slot and an 8th-level slot, as well as two feats. Since it has 13 feats, it's not a big deal. In fact, it doesn't need Mage Armor or Shield, there's just no reason why it doesn't have them - or a zillion other buffs for the matter.
This gives it a touch AC of 43 - and a flat-footed AC of 53.
Unless each wizard has an attack bonus higher than 23, they aren't hitting on anything but a natural 20. 50 Wizards will get an average of 2.5 natural 20s, but I'm going to be generous and say that they all get initiative, they're all within fifteen feet, and three of them manage to hit. They do... let's see, 22.5 damage in total. Which would be a big deal if it were more than 4% of it's hit points.
Since they're all within 15 feet of the Dragon, they've got to all be within 60 feet. The Dragon then casts
Horrid Wilting.
Assuming they all make their DC 24+ fortitude saves, they still take an average of 29.75 damage. Since the average hit points of a fifth-level NPC wizard (assuming 14 constitution) is 24, they all die. I mean, sure, one or two might live. But they're fifth level, they don't have Teleport or even Dimension Door. They're fighting an enemy that has Limited Wish and thirty-eight hit dice.
Shiny, ain't it?