Tackling an arduous portage or bushwhack on a hot, muggy day presents risks that will likely be either greatly reduced OR significantly magnified by travel in a group.

Generally speaking, it probably helps, more often than not, working as part of a team.  You can do "sanity checks" and watch out for each other.

On the other hand, the operative word is "team".  The team must move well together.  Not everyone travels at the same speed or with equal loads... especially as types of terrain vary.  When Kingfisher & I have traveled together with various parties, we have tried to level-load our portage/bushwhack crossings according to individual capabilities and the geography.  In other words, there is a portage/bushwhack plan... including an understanding of how to handle matters if things somehow go awry for one or more of the party. 

Moving without a plan can result in undue stress and risk on individual party members.  One member may try to overcompensate for others who are moving at a slower speed.  Another member may feel "pressured" to go beyond what makes health sense for him/her in order to "keep up."   For longer portaging/bushwhacking, the plan must provide for hydration needs... especially where fresh water is scarce.  I've seen/heard/participated in too many "near-miss" hydration situations on this board which could have turned real ugly fast.

Traveling with a team is the smarter way to go... especially when the group behaves as a team.  When you have to go-it alone, I recommend extreme caution; be conservative with all of your decisions.

Jimbo   8-)