I'll have to go with the poor management of matchmaking.
Now, before I continue, I'm having more fun with Halo 4 online than I ever did since Halo CE, but there are some issues that can be fixed that've already been mentioned: Sub-par maps and lack of gametypes. No one can possibly exaggerate how often Ragnarok and Exile pop up in BTIF, or how maps are too big in general. Maps like Complex do NOT belong in regular IF.
There are other smaller problems, such as Ordinances being too strong (IMO, of course), but the first two I mentioned are the biggest things.
3DS FC - 5455 9389 5386 | GT: GB2TheKitchen Ooo make it bounce, baby.
what type of super self absorbed, over demanding, under appreciative babies you all are! don't know how good you have it. don't get pissy about the DMR just because you aren't paying attention to your sight lines. SWAT is beast mode!
This includes the way they removed the awesome firefight mode and replaced it with garbage spartan ops, and then forced you to be online to even play spartan ops. Even for the "beat a spartan ops episode solo on legendary" achievement.