If you mean that you have don't have either of those as LMB, then yes, it's worth it for you to LMB them. Your first priority is to get a LMB elemental Eidolon for all elements which you might end up using (ie. have sort of teams for those elements). This is something that veteran players already have, so it's not often discussed here. But, that IS the primary purpose of the Eidolon Orb store - a catch-up mechanic for newer players who missed out previous, essential Eidolons.That's not going to happen by the looks of it.