“Use Arc energy to disrupt the protective barriers barring the way to the time gate.”
Keep with your fireteam and cross over Steps themselves. You need to get the Arc Energy into a slot that sits behind a Hydra. There is another Hydra waiting on the far side of the Steps for that needs to be dealt with as well. Because of all this, the Runner should only beak away from the Fireteam if they have an Invisibility or shielding effect ready from melee or grenades. First, on the upslope to the Gate there is a Taken Portal.
The Fireteam and Runner should take out the Hydra by the Steps and then deal with the first Taken Portal sitting on the path to the next Barrier. The fireteam should distract the Taken at this portal while the Runner jumps up the slope to quickly reach the barrier and deactivate it.
This will put the Runner within the Shadow Touched range of a Taken Portal but it is a moderately safe place as long as the Hydra is distracted. After that has been disabled, join the Fireteam and clear out what enemies you need to for the group to make it through the now open gate-way.