Tips for Campaing Legendary Halo 1 and 2?

Difficult level of these two games on legendary is kinda extraordinary compared to Halo 3, Reach and Halo 4. All i had to do was get a DMR+Plasma Pistol+ Lots of granades+ Luck and three days later i beated the game. But the enemy difficulty in the older games is annoying. Mostly because of the weapon switch speed and accuracy.

In Halo Combat Evolved the best combo i got so far was for small areas Assault Rifle+ Plasm Rile and open areas Pistol+Plasma Rifle. Even so, the old shcool sistem kinda screw the strategy up.

In Halo 2 i got my -Yoink- wrecked with any loadout i could find… mostly because elites come in hordes and they can kill you with 8 shots.

What i’m doing wrong?