Do you by any chance know that if you do co-op campaign on legendary, does this still unlock the legendary achievement? [/quote]
Yes it does, to unlock the achievement "Campaign Complete: Legendary" you must complete all 10 missions on Legendary Solo, Co-op or both. As long as when you go to select a level a Legendary shield appears on each level in either the Solo or
Co-op side or both you will have the achievement.
Yeah the Meta game achievements are much much easier solo, that way people don't steal your kills :P
I recently just did complete these and I only did it on normal difficulty with Famine, Tough Luck, Catch and Fog, and each time I easily made the required scores, if you are near the end of the level and are under the required score don't stress because
you may get a multiplier for time bonuses.
It's probably easier getting the campaign meta achievements solo. Play on Heroic, use skulls: fog, catch, famine, tough luck and you should get the points easily. If you die too much then just switch to normal. On Floodgate, Cortana and Halo activate
the Tilt skull as well.