Why are AI so useless on Legendary?

You get like 4 marines, within SECONDS they are all exterminated. And once again you are left to kill 2 wraiths, 7 elites and 15 grunts with half a clip of assault rifle.

The AI have never been useful… ever

Yeah, it seems the friendly AI in Halo 4 have taken the “Intelligence” out of “Artificial Intelligence”. I miss the good ol’ days of Reach where your Army trooper would take the Gauss turret and completely tear through any Covenant in your path.

Now, that poorly-designed Marine in Halo 4 will miss every other shot which will usually result in us taking a plasma mortar in the grill of our Hog.