And by that, I mean change the enemy.
Heroic and legendary would be far more fun if each Elite behaved like a spartan. The enemy need to be smarter, Not have more health.
At times in halo 4 the game feels like a cover based shooter. Covenant weaponry flies faster than it used to and there seems to be quite a few low walls. Legendary is quite often a difficulty where the player must hide next to some cover and use precision weaponry to remove very dangerous grunts and whittle away the shields of the elites commanding them one at a time.
i would much rather fight elites who have about as much health as they do in lesser difficulties. Grunts who die in half a second of assault rifle fire. But to be more difficult the enemy will aggressively flank, lay down suppressing fire, throw grenades quicker,take into account what weapon their enemy has, occasionally camp and most importantly coordinate with eachother. Each elite (except the minor) having access to more than one armour ability and using them well (and probably carrying more than one ability at the same time,unlike player Spartans)
Suggested additions to go with this:
Covenant Non sticky grenade and power drain. Counts as a frag/pulse grenade with a different look.
Plasma version of the hardlight shield.
covenant (possibly human) version of promethean vision. again counting as promethean vision
Regeneration field for the covenant (likely leaders)
^ these could all probably be loadout options, seeing as they are all just visually different versions of what already exists.
Perhaps a bubble shield might be a good addition. Probably not a good idea to make it a loadout item though.