A guildie shared this tip with me. It may already be on the boards here somewhere but I never ran across it.

You use the EQ button and add the port that you want to block to the blocked spells list. Then cast the port for your group.

They port, you stay.

In the backwhen, we used a similar scenario to accomplish the "Bard Gate" effect.

Druid begins to cast Circle spell, Bard begins to sing group DA song, any person(s) wishing to be ported away just click off DA at the last instant. Extremely useful !!

I wonder if this would work on succors and exodus, and I wonder if the deaggro portions would function as well. Failed egresses were at times awesome if you had a good lead on a mob.