Sadly you won't be able to hold aggro off of Relic +1 with an Ifrit weapon if the DPS are half decent.

All of our threat mods are damage % based, so the more damage you do the more threat you hold. Since there's no static threat mods besides your raw damage output, having a weapon with 7 less attack severely gimps your threat generation. If those people have relic +1 they might even have AF+1/allagan in which case you're just screwed on threat. That armor adds a lot more +str and +int than AK greens or Darklight gear, which ups their damage even further.

If they're not willing to watch their threat and tone down their damage, then it's up to them to deal with the mobs.