Archaeologists are basically rogues with spells and the ability to give themselves a luck bonus. IMO, they are strictly better than a pure rogue.
Archaeologists gain the trap sense and an ability to detect and disarm magical traps, rogue talents and advanced talents (though slower rate than standard rogue), as well as Evasion and Uncanny Dodge.
Archaeologist's Luck counts as a bardic performance for purposes of feats like Lingering Performance and gives a scaling bonus to everything save AC. Since it is a luck bonus it stacks with everything. Only downside is that it is for the bard only.
If you didn't have the rogue then it would be a perfect fit. Since you already have a rogue a standard bard would probably fit the group the best.
Depending on your group's interpretation of Weird Words the Sound Striker archetype from Ultimate Magic can be a damage beast (Extra Performance is actually better on a Sound Striker than Lingering Performance). Dirge Bard is a solid choice if you are playing in an undead heavy campaign. I see a lot of squishies in your group so an Archivist's ability to hand out insight bonuses to AC could prove very useful.