More than in previous games, a lot of balance choices for multiplayer bleed into campaign/firefight in a really bad way. The shotgun is a prime example. It has only 6 shots and takes ages to reload, not to mention being a tad too weak.

A health system based around no-bleed-through shields, which essentially gives you a bit more durability in multiplayer? Screw you, because Elites don't play by those rules and can kill you in one punch at full health and half shields.

The grenade launcher's manual fire got needlessly nerfed after the beta to the point of being useless as anything other than a vehicle EMP. The primary fire is too weak, or the total ammo capacity is too small, for the weapon to ever be worth picking up. If you need an EMP weapon, you'll never have a problem finding a (much more versatile) plasma pistol.

Needler's targeting? Elites are just going to roll away, and they never have enough ammo. The plasma launcher, also nerfed after the beta, is similarly lacking. It's pretty ridiculous how the fuel rod is so overpowered, but enemies with the plasma launcher are all but nonthreatening.

The plasma grenade's short fuse and massive blast damage is fine in multiplayer, but a complete bitch in campaign.

Vehicles are useless, unreliable trash in both campaign/firefight and multiplayer. The rocket hog in particular is a joke. Seriously Bungie, would it kill you to put in a vehicle health meter?

The pistol is too wildly inaccurate and has too small a magazine size to be anything other than a shitty DMR, instead of being a useful weapon in its own right.

I get that weapons should have some consistency between modes, but the campaign would be a lot more fun if the "noob combo" wasn't the only effective way to play.

At least the needle rifle is pretty sweet in both modes.