As you stated, the easiest way to get stuff done is with an LS though I still see pickups shouting for AF and Darkhold (on Trabia)
For the level 25 Ifrit however you'll most likely need 3 friends to help you out. If you were on Trabia I'd offer to help seeing as I've already done that fight so many times for others.
I've honestly never had a problem getting people together for level 25 Ifrit.