The One About Optimum Strategies for Co-Op Content...

As the title says, if you're having trouble with getting past the Zamboni part on Wrath of the Machine, you can slow down the timer by shooting the core on the siege engine. The core I reference is the part of the engine that glows brightly until it explodes, wiping your Fireteam. It is located if the front middle section of the siege engine, either directly to your right as you're jumping on top of the machine once you shoot the cannons off, or directly to your left as you're walking up the ramp to deliver the parts. I don't have actual statistics on how much the process is slowed, but there is a very noticeable difference on the cadence of the timer. The cadence will speed up as the timer reaches closer to zero. By shooting the core, the cadence will actually remain very nearly the same depending on the "DPS" you put out. For example, if you have only one Guardian firing at the core, the timer won't be slowed by much. But say you have three Guardians shooting the core, the timer will slow down dramatically. That being said, once all Guardians get to the siege engine with the parts, those who are not currently carrying the parts should start firing away at the core. Once the other three become exhausted, have them start shooting at the core while the other Guardians carry the part(s) to their respective places.

Anecdotal confirmation: Next to the core there are two dials similar to the dials that charge up during the first part of Vosiks. When those dials reach full, the Great White Light appears and you wipe. While shooting the core with a shotgun I have seen the dials go backwards.