Cyborg advance

Keep going men, I'm right behind you!

The idea here is to get aggressive and try to advance into the oncoming stream of covies, taking them down as you go, though you may sometimes be obliged to hold your position or fall back under the pressure, perhaps letting the Marines take the brunt of the enemy fire while your shield recharges. It's far more difficult than a fighting a static defence, and your shield will probably do a lot of bleeping, but it can be good fun, and it's a great option if you enjoy your melee attacks and a lot of up-close brawling.

Out of my way squid-face!

You can choose where you actually start things off. There's usually time to reach the base of the spiral path before enemies have come down (fly there in your Banshee perhaps), so you could start from there if you like, immediately trying to fight your way up. Alternatively you could let the enemy advance a certain way before starting your advance. You could start from right back at the underpass for example, waiting until the first covies come into view, or until they actually open fire. The further back you start, the more strung out the enemy should be, making things easier. But a lot depends on the configuration of the enemy advance.

Plasma weapons would be a good choice for this battle plan I'd say, but a rocket launcher would be handy for times when you've got a nasty concentration of enemies heading your way, or if you encounter a Hunter (they do sometimes come down the path). If you're not on Legendary an assault rifle is viable too, and can give some excellent visceral fun.

I recommend throwing a lot of grenades! While tackling a front wave with gunfire, you can be throwing grenades at enemies further back, softening up your path.